My best lifts to date are 515 on the flat and 700 on deadlifts, those are maxes of course. Now if I where to use the same weight matty used on all those exercise he posted I would certainly fall short in the reps he did on everyone of them so he has me beat hands down. Is he the strongest getbigger? Honestly, I would have to say yes from what I have seen overall, however there are a few that might be better on 1 exercise but I doubt their is someone that can best him overall.
Other notable getbiggers; Adrian and Mawse (pretty sure he has a 500 lb bench) and one guy named Billy Mimnaugh who can probably beat everyone on here on maxes, he is a powerlifter and has an 850 squat and has posted videos here of 7 plate deadlifts and 500lb good mornings
As for naturals Fortress is probably in the driver seat, but chaos has a video out of him pulling 500 for 8 reps ( no straps) and as a natural, still impressive.