Know Man was pretty uber, but his appearances are extremely limited -- he only appeared in one issue, iirc.
Anyway, he was able to effortlessly own the collective JLA:
http://i.imgur.com/TCJ8GgT.jpg
http://i.imgur.com/NAXZlGb.jpg
He sent Superman hurling into space with a gesture:
http://i.imgur.com/fSMOpOP.jpg
http://i.imgur.com/0OlSWTJ.jpg
His shielding was capable of tanking repeated strikes from a pissed-off Superman + blasts from Kyle:
http://i.imgur.com/HkLP5sW.jpg
http://i.imgur.com/qZ6hd5T.jpg
