On some top aerobatic competition planes I've seen limit loads of +/- 20G
and the aviators who fly them frequently pull 10/12g and -5/-8g [outside snaps
]
However, this is of very short duration and the practice is intense to maintain g tolerance...
Military aviators may have to pull a
Sustained 5-- 7g as some of those babies can accelerate in a 6g turn!! hence the G suit
...
for the average person more than 4.5gs is pushing it ---for the uninitiated 5gs is about it, before G-LOC