Sacrificer

Once per long rest, you may use a bonus action immediately after you hit a creature to subtract any number(up to your hit point maximum) of hit points from your current hit points. The creature you hit also takes necrotic or radiant damage(your choice when you select this feat) equal to the amount you subtracted from your own current hit points. This bypasses all resistances and immunities. You can also kill yourself with this action, and the other creature automatically dies with you.