Sentry became a superhuman when he was a high school student after he is being bullied , and so the enigmatic professor created a secret formula which he has consume it. After that he had acquired super powers and so he sewed a custome where he use this to fought enemies.He has several team ups with Fantastic Four , X-Men and the Avengers.Source here
image sourceSentry's real name is Robert Reynolds. He has super strength, super speed , invulnerability and flight. He has also psychic ability which can able to control the mind of the Hulk and calming his fury within when in rage.His power is almost limitless and we may compare this to both Silver Surfer and Phoenix.Source here