Stronger - Korg wasn't around for long, but I think strength is roughly even between Colossus and Thing, with Colossus taking a small edge in actual strength, but Thing having that heart factor that lets him keep pushing himself.
Faster - Colossus easily
More durable - Colossus has tanked a lot, even took a celestial bomb blowing a hole in his chest/back.
Better fighter - It's probably Colossus when he actually uses his skills. But most of the time they all just brawl.
Better strategist - I think this is goes to Korg. He fought pretty good in the arena, and has some military training I believe.
Thing is not faster than Colossus.
Nor is he stronger. They're even if anything, with Colossus naturally having somewhat of an edge due to the densest natural occuring metal being >>>> rock.
Pete has also shown massive fighting skills especially when armored by using a mix of his enhanced speed and fighting skills. Most of Ben's fights are him brawling.