Reaper of the Mephidross

Deathtouch
Infect (This creature deals damage to creatures in the
form of -1/-1 counters and to players in the form of
poison counters.)
Whenever a creature an opponent controls dies,
if it had a -1/-1 counter on it, Reaper of the Mephidross deals 1 damage to that creature's controller and that player discards a card.