Vrael Bloodhound

Haste, Envenom (whenever this creature deals
damage to a creature, player, or planeswalker, put a
number of poison counters on that creature, player, or planeswalker equal to this creature's power.)
Whenever Vrael Bloodhound deals damage to a
player, if that player has one or more poison
counters on them, it deals twice the damage
instead.