Grudge-Blade Oni

Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)

When this creature dies, target opponent loses life equal to its power.

Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Even the noblest soul can become corrupted.