Crusader

Unholy Slayer 1 — Gets +1/+0 when blocking
or blocked by black creatures.
Veterancy — At the end of combat, if this creature
dealt lethal damage to an opponent's creature for
the first or third time, it gains +0/+1 and +1/+1 respectively.
{1}{w}: Crusader gets +0/+1 until end of turn.
(Activate this ability only once per turn)
"A mighty sword arm anchored by holy purpose -
a zealous warrior!"