#Divine smite 5e plus

Hexblade Paladins are also really good since they get to recover 5th level spell slots every short rest so you can divine smite a lot more. Sorcadins (Paladin and Sorcerer multiclass) are particularly brutal because you get better spells and more spell slots to burn. Everything is an automatic critical if the target is paralysed such as from a Hold Person or Hold Monster spell which doubles all damage. This damage is stackable with weapon damage and anything you do to add to attack damage like from certain bonus action spells, Holy Weapon, the effects of a magic weapon, and so on.

You could use action surge to make 4 attacks, each attack spending a 4th or 5th level spell slot dealing 5d8 damage each for a total of 20d8 divine smite damage (24d8 versus undead or fiends). You will have 2x 4th level spell slots and 1x 5th level spell slots. Let's say you were 18th level Paladin and 2nd Level Fighter.

You have 2 attacks from 5th level onwards and you achieve the maximum damage with a spell slot of 4th level or higher.

#Divine smite 5e plus

The divine smite damage is 1d8 plus 1d8 per level of the spell slot used to a total maximum damage of 5d8 and this increases by 1d8 against creatures that are undead or fiends. As stated by Lunali you can use one spell slot per attack.