This guy has been pretty amazing. I edited him quite a bit, but a .500 average for a whole season is still pretty impressive, despite the use of PEEs (Performance-Enhancing Edits). And before you ask, the league is on your basic 1997 settings. He was actually created as an experiment in how good a guy could be if you edited him to near-maximum levels. An OOTP Frankenstein, if you will.
As far as unedited guys go, Todd Robbins has put up some eye-popping numbers for Buffalo: