The Sentry is effectively Marvel Comics own resident Superman, as he shares a number of the same powers with DCs Man of Steel, with the added benefit of not having a clear weakness. With kryptonite, anyone can take Superman down, but there is no equivalent for Sentry. However, that isnt to say Sentrys invincible, as a being who is strong enough can absolutely defeat Marvels Superman in battle. In fact, there are more than a few heroes and villains alike who not only could beat Sentry, but canonically have.