Bloody Hands (5e Class Feature)
From D&D Wiki
This optional class feature replaces Lay on Hands.
Many paladins are holy healers, but your soul yearns to kill. You have a pool of murderous power that replenishes when you take a long rest. With that pool, you can deal extra necrotic damage equal to your paladin level times 5. Whenever you deal or expend damage from this pool, you also take half that much damage.
When you hit a creature and deal damage, you can draw power from the pool to deal extra damage to that creature, up to the maximum amount remaining in your pool. You can apply this extra damage after you see your damage roll result.
Alternatively, you can expend 10 extra damage from your pool to wreath your weapon in murderous energy, allowing your next weapon attack to ignore its target’s damage resistances and immunities.