The Man-Beast is one of many artificially evolved animals (Man-Beast being a wolf evolved into bipedal human-like form) created by the High Evolutionary. The High Evolutionary was attacked by Thor while Man-Beast was being altered, which caused for him to remain in the evolving solution too long; resulting in him being 'too perfect' and giving him a hatred of all forms of life.
Man-Beast turned on his creator and made his own army of Ani-men. Man-Beast and his army came into conflict with Thor and their creator and were defeated; being sent into deep space in a rocket. They later found their way back; invading the High Evolutionary's counter-earth and corrupting it. The High Evolutionary sent Adam Warlock after the Man-Beast and after a lengthy war that also brought in the Hulk from Earth to fight alongside Warlock, the Man-Beast was beaten again.
Over the years since then, Man-Beast has fought Warlock and Thor on numerous other occasions; often fighting Thor alongside his ally the Bi-Beast.
The Man Beast took on a new identity as the Omega and formulated a plan to capture the Infinity Gems
for himself. With the Infinity Watch
just beginning it's protection of the gems, the Omega was able to capture all of them except his nemesis Adam Warlock. Using the gems he had, Omega created a energy monster to defeat his old enemy, but Warlock tricked it into destroying the ship, forcing the Man Beast to escape without the gems.
On one occasion, Man-Beast infiltrated human society disguised as a United Nations politician named Senator Kyle Munson and was the driving force behind getting the U.N to try to invade Monster Island where Warlock and the Infinity Watch were still residing. He telepathically controlled the Avengers to attack the Infinity Watch, but Vision was able to resist this control. Vision informed the others of the mind control and Moondragon was able to free them with her Mind Gem. Warlock went to the United Nations and confronted the Senator, revealing him to be the Man Beast and nearly beating him to death before Captain America and the Avengers pulled Warlock off of him. He was taken into custody by the Avengers.
The last time that the Man-Beast appeared, The High Evolutionary finally managed to de-evolve him back into a normal wolf with the help of Quicksilver.
On multiple occasions when the Man-Beast was battling Thor (after their initial encounters) and Warlock (with the Infinity Watch), Man-Beast was referring to himself as Karnivore.