What is the max damage I can do with a 20th-level greatsword-wielding melee Hexblade Warlock?

Question

I'm looking for a highly-optimized endgame (20th level) melee build, abusing Elven Accuracy and Hexblade's Curse to deal as much damage in a single turn as possible. Criteria are as follows:

• Assume the PC's Charisma is 20 with the Elven Accuracy feat (choosing Charisma) and the Half-Elf racial Ability Score Increase.
• The PC must use Elven Accuracy and Hexblade's Curse, with melee attacks from a Pact Greatsword.
• A setup round is permitted.
• All resources will be consumed in the attack turn for maximum damage.
• No magical items or boons.
• Assume target is Large or smaller for the purposes of Eldritch Smite knocking them prone.
• No Unearthed Arcana.
• No external aid (such as an ally casting haste).
• I would like to avoid low-probability effects such as Wild Magic Surges; the goal is to lean toward consistency.

Currently, with a planned setup of Battle Master Fighter 12 / Hexblade Warlock 8, I am able to gain advantage on all attacks (thanks to Feinting Attack and Eldritch Smite) and deal 12d6+5d10+10d8+132, for an average of 246.5 damage in a single turn after the setup round. This calculation assumes all of the attacks hit, and none are critical hits. The expected damage is likely higher due to the expanded critical range of Hexblade's Curse, and the broken Elven Accuracy "triple advantage".

As stated earlier, the only core feature is that it is a melee-oriented Hexblade Warlock, and utilizes Elven Accuracy.

Answer 1

David laid a lot of great foundation here, but I think I found a few ways that we can improve on this a bit.

1) Use a "Hold X" spell. This spell is going to be your best friend. This is because they are paralyzed which means that a) you attack with advantage and b) any attack that hits will CRIT automatically if the attacker is within 5 feet. While gaining advantage and using your Elven-Tri-Vantage and Hexblade's curse is fun, how would hitting a CRIT on an 18, or a 17, or a 16, or a (…) also feel? Because of this, I feel that you can go SUPER-NOVA with this spell.

2) Go Whispers Bard. You can get 2x attacks via Warlock invocations and you basically get a "sneak attack" of psychic damage with Psychic Blades.

3) Not trying to bash at all, but ensure you get your Ability Scores correct here. I get that it says assume that the CHA is 20, but the only way that would happen with David's approach would be to randomly roll your stats and get a 17 or an 18 on the rolls. Otherwise, with David's approach you can only get a +4 CHA with point buy or standard array, so the max would be 361.292 (I think I did that right???...). I have noted that in my builds and have accounted for it appropriately (hopefully)...

With that, I may I present to you

The Hold-CRIT SUPER-NOVA Build

Half-Elf - 13+/x/x/x/x/17 stat priority

Hexblade Warlock 5 (1 ASI)

• Hexblade's Curse [HBC]
• Pact of the Blade (@3)
• Elven Accuracy, CHA + 1 (@ 4)
• Eldritch Invocations
  • Thirsting Blade (2x attacks per action)
  • Improved Pact Weapon [IPW]
  • Eldritch Smite

Paladin 2

• Great Weapon Fighting [GWF] (reroll 1s and 2s on sword damage)
• Divine Smite

Fighter 3

• Action Surge (@ 2)
• Battle Master (@ 3)
  • Tripping Attack

Whispers Bard 10 (2 ASIs)

• Psychic Blades (@ 3, increases @ 10)
• Hold Person (@ 3)
• CHA +2 (@ 4)
• Hold Monster (@ 7)
• Great Weapon Master [GWM] (@ 8)

Round 1: Setup Round

Action: DC 19 Hold Person/Monster

Bonus Action: HBC

Round 2: Kill Round

Action: Attack x2

Action Surge: Attack x2

Bonus Action: Great Weapon Master Attack

You only get this bonus attack if you CRIT (which you do with Hold Person/Monster)

If you succeeded in holding the person, JUST GO HAM.

If you didn't, you have 2 options on your first hit (not at advantage):

• If you think the BBEG can succeed an 8 + PROF + DEX/STR saving throw, burn Eldritch Smite ASAP to get ADV on attack
• Otherwise trip him with that saving throw from Tripping Attack & get ADV on attack

Each Attack is as such: (^ => While Supplies Last, you only have 4)

   = 2d6[GWF] + 5 (CHA) + 1 (IPW) + 6 (HBC) + 10 (GWM)
     + 5d8 (Divine Smite)
     + 1d8 (Tripping Attack)^
   = 2d6[GWF] + (5+1^)d8 + 22 [+2d6[GWF] + (5+1^)d8 iff CRIT]
   = 8.333 + 22.5 + 4.5^ + 22 [+ 8.333 + 22.5 + 4.5^ iff CRIT]
   = 52.833 + 4.5^ [+ 30.833 + 4.5^ iff CRIT]

With an additional 1-time per round NOVA of additional damage:

     + 4d8 (Eldritch Smite)
     + 5d6 (Psychic Blades)
   = 18 + 17.5
   = 35.5 [+ 35.5 iff CRIT]

The Numbers

All calculations are assuming that you hit all attacks... didn't have an AC to run this against

50% chance BBEG fails the save with a +8 modifier. Auto CRIT on all hits. That gives us:

   = 5 * (Attack CRIT) + 4 * (Superiority Dice) + (NOVA CRIT)
   = 5 * (52.833 + 30.833) + 4 * (4.5 + 4.5) + (35.5 + 35.5)
   = 5*83.666 + 4*9 + 71
   = 525.333

50% chance BBEG succeeds save with a +8 modifier. The damage gets a bit more complicated with CRIT-fishing

   First Attack:
      1) You may want to make this attack without the -5 penalty so that you ensure more chance of a hit.
      2) The first attack has a 10% chance of CRIT (not at advantage).
      3) Use a Combat Superiority Die
      4) Damage output Expected:
         => 52.833 + 4.5 + (-10 if you didn't take the -5 penalty) + (10% of [30.833 + 4.5])
         => 57.333 + 3.533 + (-10)
         => 50.866
      4) We will say for this you didn't use Eldritch Smite, but tripped with Tripping Attack & is prone
   Next Attacks (3)
      1) These are made with Tri-Vantage, which is 27.1% chance
      2) Use the -5 penalty because Tri-Vantage.
      3) Use the rest of the Combat Superiority Dice
      4) Expected Damage from attacks:
         => 3 * (52.833 + 4.5 + (27.1% of [30.833 + 4.5]))
         => 3 * (57.333 + 9.575)
         => 3 * 65.214
         => 200.724
   Was there a critical hit? 
      1) we rolled 10 times, and could CRIT on a 19 or a 20
      2) this is a 65% chance of at least 1 CRIT and 35% chance of no CRITs
         a) https://dice.clockworkmod.com/
         b) (d20 > d20 > d20 > d20 > d20 > d20 > d20 > d20 > d20 > d20) ac 19
      3) we would take this on to the end even if we didn't CRIT, so add that
      4) Extra Damage from NOVA Calculation:
         => 65% of (CRIT Dmg) + 35% of (Normal Dmg)
         => (65% of 71) + (35% of 35.5)
         => 46.15 + 12.425
         => 58.575
      5) If we CRIT, we would get an extra Bonus attack
      6) Extra Bonus Action Attack Damage Calculation @ Adv
         => 65% of (52.833 + (27.1% of [30.833]))
         => 65% of (52.833 + 8.356)
         -> 65% of (61.189)
         => 39.773
   Putting that all together we get:
      => 50.866 + 200.724 + 58.575 + 39.773
      => 349.938

Now putting All Options together:

   => 50% of (Fail Damage) + 50% of (Succeed Damage)
   => (50% of 525.333) + (50% of 349.938)
   => 262.6667 + 174.969‬
   => 437.6357

But I'm not done yet. While the above build is cleaner, I think I'd prefer to play this variation of it (Does take more setup pre-encounter!).

High Consistency Hold-CRIT SUPER-NOVA Build

NOTE If you don't need Hold Monster, drop a level of Sorcerer and pump bard up to 4 for an additional ASI. This will up the DC of "Hold X", which will push the frequency of you succeeding by about an additional 3% or so.

Half-Elf - 13+/x/x/x/x/17 stat priority

Shadow Sorcerer 6 (1 ASI)

• Quickened Spell (@3)
• GWM (@ 4)
• Hound of Ill Omen (@ 6)

Hexblade Warlock 9 (1 ASI)

• Hexblade's Curse [HBC]
• Pact of the Blade (@3)
• Hold Person (@ 3)
• Elven Accuracy, +1 CHA (@ 4)
• Eldritch Invocations
  • Thirsting Blade (2x attacks per action)
  • Improved Pact Weapon [IPW]
  • Eldritch Smite
• Hold Monster (@ 9)

Paladin 2

• Great Weapon Fighting [GWF]
• Divine Smite

Fighter 3

• Action Surge (@2)
• Battle Master (@ 3)
  • Tripping Attack

PRE-BATTLE SETUP

Take 2 Hours & convert Pact Slots into Points and into 4th Lvl Sorc Slots. Each hour will net you 2 4th level slots. This will get you enough slots to smite each time you need to @ max level with divine smite

Round 1: Setup Round

Bonus Action: Place Hound of Ill Omen by target

Action: DC 19 Hold Person/Monster @ Disadvantage (b/c of Hound of Ill Omen)

Round 2: Kill Round

Action: Attack x2

Action Surge: Attack x2

Bonus Action: Great Weapon Master Attack/HBC

You only get this bonus attack if you CRIT (which you do with Hold Person/Monster)

If you succeeded in holding the person, JUST GO HAM.

If you didn't, you have 2 options on your first hit (not at advantage):

• If you think the BBEG can succeed an 8 + PROF + DEX/STR S.T., burn Eldritch Smite ASAP to get ADV on attack
• Otherwise trip him with that S.T. from Tripping Attack & get ADV on attack

Each Attack is as such: (^ => While Supplies Last, you only have 4)

   = 2d6[GWF] + 5 (CHA) + 1 (IPW) + 10 (GWM) 
     + 5d8 (Divine Smite)
     + 1d8 (Tripping Attack)^
   = 2d6[GWF] + (5+1^)d8 + 16 [+2d6[GWF] + (5+1^)d8 iff CRIT]
   = 8.333 + 22.5 + 4.5^ + 16 [+ 8.333 + 22.5 + 4.5^ iff CRIT]
   = 46.833 + 4.5^ [+ 30.833 + 4.5^ iff CRIT]

With an additional 1-time per round NOVA of an additional

     + 6d8 (Eldritch Smite)
   = 27 [+ 27 iff CRIT]

EXTRA BONUS ROUND: Doggo’s Attack Round

Depending on where the hound is in initiative, it may get 2 of these rounds, but probably only 1

Action: Bite

   = (2d6) + 3 [+ 2d6 iff CRIT]
   = 7 + 3 [+ 7 iff CRIT]
   = 10 [+ 7 iff CRIT]

The Numbers of it all

All calculations are assuming that you hit all attacks... didn't have an AC to run this against

75% Chance BBEG fails this save with a +8 Modifier. Auto CRIT on all hits. That gives us:

   = 5 * (Attack CRIT) + 4 * (Superiority Dice) + (NOVA CRIT) + (Doggo CRIT)
   = 5 * (46.833 + 30.833) + 4 * (4.5 + 4.5) + (27+27) + (10 + 7)
   = 5*77.666 + 4*9 + 54 + 17
   = 495.333

25% Chance BBEG succeeds the "Hold X" save with a +8 Modifier. If this happens Cast HBC to help with CRIT fishing.

   First Attack:
      1) You may want to make this attack without the -5 penalty so that you ensure more chance of a hit.
      2) The first attack has a 10% chance of CRIT (not at advantage).
      3) Use a Combat Superiority Die
      4) Damage output Expected:
         => 46.833 + 4.5 + (-10 if you didn't take the -5 penalty) + 6[HBC] + (10% of [30.833 + 4.5])
         => 57.333 + 3.533 + (-10)
         => 50.866
      4) We will say for this you didn't use Eldritch Smite, but tripped with Tripping Attack & is prone
   Next Attacks (3)
      1) These are made with Tri-Vantage, which is 27.1% chance
      2) Use the -5 penalty because Tri-Vantage.
      3) Use the rest of the Combat Superiority Dice
      4) Expected Damage from attacks:
         => 3 * (46.833 + 4.5 + 6 + (27.1% of [30.833 + 4.5]))
         => 3 * (57.333 + 9.575)
         => 3 * 65.9.9
         => 200.726
   Was there a critical hit? 
      1) we rolled 10 times, and could CRIT on a 19 or a 20
      2) this is a 65% chance of at least 1 CRIT and 35% chance of no CRITs
         a) https://dice.clockworkmod.com/
         b) (d20 > d20 > d20 > d20 > d20 > d20 > d20 > d20 > d20 > d20) ac 19
      3) we would take this on to the end even if we didn't CRIT, so add that
      4) Extra Damage from NOVA Calculation:
         => 65% of (CRIT Dmg) + 35% of (Normal Dmg)
         => (65% of 54) + (35% of 27)
         => 35.1 + 9.45
         => 44.55
   Now your Doggo gets to attack
      1) Pack Tactics, so it gets advantage (9.75% chance of CRIT)
      2) Doggo Damage Calculation
         => 10 + (9.75% of 7)
         => 10 + 0.683
         => 10.683
   Putting that all together we get:
      => 50.866 + 200.726 + 44.55 + 10.683
      => 306.825

Now putting All Options together

   => 70% of (Failed Save) + 30% of (Succeeded Save)
   => (70% of 495.333) + (30% of 306.825)
   => 340.433 + 89.187
   => 429.620

Cool Notes:

1) An upwards of an extra 25% chance to succeed on your "Hold X" spell which benefits the rest of the group MAJORLY.

1.a) This can be an even greater difference if you have a Rod of the Pact Keeper, as those increase Warlock Spell Save DCs as well!

2) You gain the advantage of a SorLock here, so you can prep for a few hours and gain additional spell slots for “extended NOVA-ing”

2.a) You could even push through a long rest, forgoing your Sorc slots back and risking a point of exhaustion to do nothing but convert Pact slots to Sorc Slots, up to 16 4th level slots!!! Check if your DM will allow it first though.

2.b) My breakdown "Everyday Exhausted" breakdown here would be:

  9 x 1st (shield and stuff)
  6 x 2nd (misty step / mirror image)
  10 x 4th (Armor of agathus/smite) 

3) You can still HOLD-NOVA without a prep round

• Bonus Action: Quicken => "Hold X"
• Action: Attack x2
• Action Surge: Attack x2

Conclusion

I have way too much time on my hands... Hope this gives y'all some more ideas to really push this to yet another level!

Answer 2

The highest expected damage is 366.292

The Character

Carolinus, the half-elf in question has the following classes:

• Warlock (Hexblade) 5 ------- (for Hexblade's Curse, Pact of the Blade, Improved Pact Weapon, Eldritch Smite, and 1 ASI)
• Bard (College of Swords) 10 - (for Blade Flourish, Extra Attack, spell slots, true strike and 2 ASI)
• Fighter (Battlemaster) 3 ----- (for Action Surge and Combat Superiority)
• Paladin 2 ---------------------- (for Divine Smite)

...and the following feats (in exchange for ASIs)

• Great Weapon Master
• Elven Accuracy
• Martial Adept

The Preparation

For the preparation round, Carolinus uses his action to cast true strike and his bonus action to use Hexblade's Curse.

The Turn

Carolinus' turn follows this procedure:

• Take the Attack action.
• Perform one attack with the pact greatsword (advantage due to true strike).
  • Use Great Weapon Master's second benefit.
  • Use Tripping Attack to knock the target prone.
• Attack again in the same way (advantage due to prone)
• Use Action Surge.
• Take the Attack action.
• Attack twice more in the same way as before.
• Use Blade Flourish and Eldritch Smite on the first critical hit, or on the last attack if there are no critical hits.
• If any of the attacks are a critical hit, immediately make another attack again in the same way with a bonus action using Great Weapon Master's first benefit.

The Calculation

Since we are assuming attacks hit, we are guaranteed an average damage of 252.

• This comes from four attacks which equal 2d6 (Greatsword) + 5 (Charisma) + 1 (Improved Pact Weapon) + 6 (Hexblade's Curse) + 10 (Great Weapon Master) + 5d8 (Divine Smite) + 1d8 (Combat Superiority: Tripping Attack)
• And finally a Blade Flourish and Eldritch Smite on one of the attacks for +1d10 + 4d8

...from there we are only concerned with critical hits which provide the chance to improve damage:

• Each of the attacks from the Attack action have a 27.1% chance of being critical hits, which would increase the damage by 2d6 + 5d8 + 1d8 (or an average of 34)
• You also get an extra 1d10 + 4d8 from the Blade Flourish and Eldritch Smite (which should be saved for the first critical hit).
• This makes the overall expected damage for the four attacks go to 285.73.

...finally, if any of the attacks are critical hits, we get the bonus action attack with an expected damage of:

• 2d6 (Greatsword) + 5 (Charisma) + 1 (Improved Pact Weapon) + 6 (Hexblade's Curse) + 10 (Great Weapon Master) + 5d8 (Divine Smite) + 1d6 (Martial Adept: Tripping Attack)
• +2d6 + 5d8 + 1d6 on a critical hit.
• One more chance for a critical hit for Blade Flourish.

With the last attack accounted for, our expected damage is 366.292

Answer 3

The best I found so far is: Hexblade 7, Swordbard 8, Battlemaster 3, Paladin 2

That way you are looking at a total of 8d6+30d8+88, which averages at 251, ignoring crits and misses.

You use your ASI to get Elven Accuracy, Great Weapon Master and to get Cha to 20. You need Eldritch Smite and Improved Pact Weapon as invocations. You need Feinting Attack and any manoeuvre that you can add to your regular attacks.

In your preperation round you summon your pact greatsword and apply hexblades curse.

In your attack round you start with feinting attack and then take your 4 attacks. You get:

• 4×(2d6+6) from your weapon
• 4×10 from great weapon master
• 4×6 from hexblades curse
• 4d8 from manoeuvres
• 5d8 from eldritch smite
• 4×5d8 from divine smite
• 1d8 from blade flourish