How much damage does my Hexblade Warlock deal with their Bonus Action attack?

Question

I built a simple level 3 Hexblade warlock with 18 Charisma. This is a scenario that I went through in our first encounter:

1. I created a Hex warrior weapon: a shortsword.

2. I also created another Pact weapon: another shortsword.

3. I cursed a target using my Hexblade's curse using my bonus action in round 1.

4. If I held my Pact weapon shortsword in my main hand, I could potentially do 1d6 +4 +2 damage in round 2, if I successfully hit the target.

5. Then I could use the Hex warrior weapon shortsword, as my off-hand weapon to do another 1d6 +4 +2 damage using my bonus action in round 2, again, if I successfully hit the target.

I was told I could not do this, and my off-hand weapon would only do 1d6 damage as I did not have the Two-weapon fighting style of a fighter.

Was I mistaken when adding my bonuses to the off-hand weapon attack using my Hex warrior weapon?

Answer 1

You get to add the Hexblade Curse Damage, but not the Ability modifier damage to your bonus attack

Your hexblade curse damage is independent of the weapon you attack with, it applies to all attacks against the selected target (XGtE, p. 55), so you get the +2 to your bonus action attack from two-weapon fighting.

You gain a bonus to damage rolls against the cursed target. The bonus equals your proficiency bonus.

Two-weapon fighting (p. 195 PHB) works like this:

When you take the Attack action and attack with a light melee weapon that you’re holding in one hand, you can use a bonus action to attack with a different light melee weapon that you’re holding in the other hand. You don’t add your ability modifier to the damage of the bonus attack, unless that modifier is negative.

Since you make the second attack as a bonus action attack with two-weapon fighting, and since your ability modifier at +4 is not negative, it does not get added to your bonus action attack.

Thus, the bonus action attack deals 1d6 +2 damage.

The fighter’s Two-Weapon Fighting style says

When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack.

Therefore, you would deal 1d6 + 2 + 4 damage only if you also had this fighting style, as your DM told you.

Answer 2

The second attack doesn't get the +4

Player’s Handbook, pg. 195:

When you take the Attack action and attack with a light melee weapon that you’re holding in one hand, you can use a bonus action to attack with a different light melee weapon that you’re holding in the other hand. You don’t add your ability modifier to the damage of the bonus attack, unless that modifier is negative. If either weapon has the thrown property, you can throw the weapon, instead of making a melee attack with it.