Buster Rancher

Whenever equipped creature blocks or becomes
blocked by a creature, it gets +3/+3 until end of
turn for each creature it blocks or blocking it
beyond the first and only if those creatures
power and toughness is greater than than
equipped creature's base power and toughness.
Equip {3} ({3}: Attach to target creature you
control. Equip only as a sorcery.)