Sentry

About this guy, Iron Man said that he has no physical weaknesses – we can believe him, since Sentry can come back from the dead (even more than that, he can also bring them back to life).

Sentry was just a usual guy (Bob Reynolds, middle aged and a bit chubby) until he a super-serum changed him. After that, all of his molecules were able to move an instant ahead of the timeline – it is, however, revealed that the serum is just the recipient of a sentient life force from another universe, thus explaining the colossal power of Sentry.

So, besides his incredible regenerative ability and besides the usual superpowers superheroes possess, Sentry is also capable of light-speed flight, has very acute senses (being able to hear a butterfly on the other side of the world), is a very powerful telepath (his telepathic powers dwarf those of Professor X), can phase through objects, can become invisible and can shapeshift.

He is one of the superheroes who is basically immortal – his regenerative ability would prevent him, even if he tried to commit suicide. Why would he do that? Because he is mentally unstable and he is highly susceptible of having his mind invaded.

As a more explicit feat of strength, Sentry fought with the Hulk until both of them tired and reverted to their human forms – only afterwards Bruce Banner knocked down Reynolds.