2. He's The Big Gun They Need
Despite his negative qualities and the risk associated with having Sentry in tow, when there's a threat that even the likes of Hulk, Thor and Iron Man can't handle, Sentry is the kind of guy you want helping you out. In the comics, he is said to have fought Galactus to a stalemate - Galactus being the devourer of planets and a character capable of destroying galaxies. He has defeated the Molecule Man at his own game (matter manipulation) - and bearing in mind Molecule Man is a MASSIVELY powerful character, this is no mean feat. He's powered through the Crimson Bands - a powerful magic restraining spell which the likes of the Hulk have failed to escape from. He has destroyed a planet with his energy flares, which can also be seen in the normal world whilst he is in a microverse, which is an INSANE feat of power. When a guy like Thanos comes to Earth and the Avengers are completely out-gunned, only someone like the Sentry wouldn't be swatted aside like a fly. If Marvel want Thanos to have someone capable of at least standing up to him, there are few more powerful Earth-based superheroes than Sentry.