I wanna say Power Girl, but as of Dark Avengers 12 or 13, Sentry became VERY broken. He has the ability to control molecules now?! Sorry, if that's the case, Power Girl can't stand up to that. And after what he did to Ares in Siege #2, yeah, Sentry has got this one.
GL would win. Venom is badass don't get me wrong, but he is a little bit more brute strength while Hal Jordan (and most all other GLs) is little strategic. Plus, GLs can pretty much make any object with their ring. Combine that, with strategy and an amazing amount of sheer willpower, GLs will win over Venom.
@War Killer: Yeah, I read the first issue of Ult. Armor Wars, it was really good, I don't know why I haven't picked it up the rest yet. Ultimate X is a very good comic, I recommend it. Loeb did a really good job on that one. And as for Ultimate Enemy goes, I thought it was a pretty awesome issue, but it did start a bit slow. I'm a Bendis fan, so I'll be getting the next issues most def. Check out my review of Ultimate Spidey #7!