When Mir was doing commentary, he always put over Joe Stephenson as having tremendous power, especially in his guillotine. For Mir, a guy known for having some serious crushing strength in submissions, to say that about someone he outweighed by about 100 pounds---I always thought that was a pretty strong endorsement.
A lot of fighters have called Ken Shamrock the strongest guy they've ever trained with. Not that he doesn't also look like a strong guy, but fighters who have said that have put Ken above even bigger guys like Lesnar, Monson, Coleman, etc.