Sure if The Sentry can somehow control reality which he might since he brought his dead wife back from the dead he might be able to beat Doomsday, but if its just the powers that The Sentry uses most of the time and not whatever he used to bring his wife back he also might be able to beat Doomsday to death or something like that but Doomsday would just come back and stomp him into dust.
@ghostravage: After the debate with Mr.Master on the other thread, i am waiting for Brian Michael Bendis to reply to my question about whether Molecule Man was , for whatever reason, depowered for the purpose of the story. I'll wait till he replies, and then make a case from there on.
As per molecule man, here is the whole chronology of post retcon molecule man i created a while back: http://www.comicvine.com/molecule-man/4005-11880/forums/post-retcon-molecule-man-chronology-755744/
Stable sentry wins. At the very least he can incapacitate Doomsday for quite some time with his reality manipulation exceeding that of half a cosmic cube(possibly the most powerful one, considering it is made up of post-retcon MM and Beyonder), and survive an extended period against his blows. Doomsday, after being one-shotted by Imperiex needed Luthor's help to grow back, so he can die as well.