Man-Eating Cow

Yes, this is real. It is from The Tick comic and got a spin-off series (although I can't find any info on it).
Biography
Chairface Chippendale trained Man-Eating Cow to eat people. She was kept in pit with other man-eating cows and alligators. The idea being that Chairface would throw in the pit people he wanted to get rid of and the animals would eat them. The cows and alligator turned on each other (since, according to issue 7, "the alligator is the cow's natural-born enemy") and Man-Eating Cow was the only survivor. After Chairface was sent to prison, the police tried to transport the cow away, but it escaped. The cow ate two trigger men trying to kill the Tick. When the Tick and Arthur decided to go to New York, the Tick left the City in the Man-Eating Cow's "hands". Since then, the cow has been a superhero by eating criminals.
Powers
The Man-Eating Cow is tougher and stronger than a normal cow. She has seem to have some form of super-eating powers as she ate "through an inch-thick steel cable" (The Tick issue 8) and can eat humans at abnormally fast speed.
References:
http://www.comicvine.com/man-eating-cow/4005-41614/