Kerr, Radioactive Instructor

Gross. (This creature can't be blocked by creatures
with counters on them.)
At the beginning of your upkeep, put a Toxic
counter on up to three different creatures you
don't control.
Creatures your opponents control get -1/-1 for
each Toxic counter on them.
Kerr can't attack unless you're wearing the color
green. (Glasses and Jewelry don't count.)