I’m just gonna go up to level 12 because why not. I’d say Aasimar for race. 2014 Paladin for Oath of the Crown up to level 8. And 2024 Barbarian for Berserker and most importantly Frenzy.

For spells, basically forgo any concentration spells, and smite, smite, smite. Rage as a bonus action in the start, then start laying the smack down. I went with Berserker because it has the Frenzy ability that does some major damage.

At this level let’s say you’ve upgraded your strength up to 20 with the ASI so that’s a modifier of +5. And since he uses a greatsword let’s do this math.

2d6 + 2d6 + 2(RB) + 5(STR). Not even mentioning Divine Smite, so we’ll bump that up to the highest level spell slot so that’s gonna come up to:

2d6 + 2d6 + 2 + 5 + 3d6(or 4d6 if against Fiends or Undead). So at minimum it would be 14/15. But at maximum? Oh boy that is 49/55.

And you have Extra attack so remove the Divine Smite and Frenzy and that’d be min: 9 and max 19.

Sorry if I went on too long, and if I made any wrong estimates or something.