Who would you consider is the most feared fighter to be inside of his/her guard? Who is most likely to submit someone from the bottom? With the evolution of the ground game it seems submissions from within the guard (in MMA) are few and far between...
Also, NO HOMO...
Jobe Watson's New and Improved Butler -
The correct answer is GSP. But since nobody can stop his takedowns, he has never had to show it.
GSP's bottom game is actually superb. Submissions aren't a big part of it, though. Aoki is a good choice because he attacks from the bottom with unmatched aggression, but I'd also say Frank Mir because he doesn't let go until you're damaged.
Pettis n Diaz attack a lot from backs
these days i dont think anyone is scary from their back.
Damien Miai, frank Mir, Big Nog, Werdum, condit has pretty nasty sweeps too
I enjoy watching Pettis and Cerrone fight off of their backs. They're always attacking, rather than closing their guard till they get a stand up.