Divine Smite

When you hit a creature with a melee weapon attack, expend one paladin spell slot to deal 2d8 radiant damage, in addition to the weapon's damage.
-2nd lvl Spell Slot= +3d8
-3rd lvl Spell Slot= +4d8
-4th lvl Spell Slot= +5d8 (max)
The damage increases by ld8 if the target is an undead or a fiend.