Sentry is a vast, powerful cosmic hero from Marvel comics but he is far from perfect - in fact he is constantly depicted as amongst the most dangerous of Marvel's anti-heroes and has went into full-scale villainy on numerous occasions, in part due to his character being about the struggle of a generally "omnipotent" being to stay good or even neutral - he is also extremely prone to mental breakdowns and terrifying violence.

Like many powerful heroes in Marvel he's also fallen victim to Apocalypse and became one of his Horsemen, he is also in a continual fight against his psychotic half made real, the demonic entity known as the Void.