Chickens are one of the most elite fighters in the animal kingdom lbs for lbs. That's not a joke. They have huge sharp spurs on their feet they dig into their adversaries with surgical precision. Even with a big size advantage a penguin would be opened up like a can of soup in no time at all.
But penguins are cold-hearted and evil.
http://www.crazyclips.co.cc/videos/evil-mother-penguin/index.htm