Envy

You may have Envy enter the battlefield as a copy
of a creature an opponent controls, except its
name is Envy, it's legendary in addition to its
other types, and it has "{2}{u}, Discard a card:
Return Envy to its owner's hand." and evolve.
(Whenever a creature enters the battlefield under your control, if that creature has greater power or toughness
than this creature, put a +1/+1 counter on this creature.)

Resentment Made Flesh, Covetous Queen, First and
Last of the Sins.