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