Joe Fixit would beat the shit out of Thing/Colossus level beings. Thing would need to be amped to Pineapple levels to stand a chance, and even then, he'd lose the majority.
Joe Fixit was still taking down the likes of the Absorbing Man even at his lower base levels of strength.
He's a pretty cunning and dirty fighter, he has a win over Pineapple Thing when he used his smarts to beat him but did get pounded by Pineapple Thing in their first fight.
Ben needs to take him out fast if he takes him out at all, I think it would make for a good fight.
Ben has a big heart; sometimes, though, writers make a bogger thing of his never say die attitude. It's like Rocky, if Ben has survived a beating and is saying something like, "must save Suzy" as he crawls towards his opponent, the closed box often states "Ben Grim's heart and fighting spirit gives him a chance despite his body taking blah bla blah". Now; if, Ben get's up and get's to say it's clobberin time etc.... This is the heart scenario.