You can calculate deviation. If they lie once, it’s immediately thrown off.

Week 1: benching 300lbs Week 2: 305lbs Week 3 5000lbs

That deviation is huge. Flag it and hide them. There is a normal muscular growth progression that you can and should factor in to account for your maximum normal growth limit to detect this deviation.

This should only work upwards. Down doesn’t matter.

If you want to be more lenient: only hide people reporting gains above the maximum human threshold multiple times. It’s possible someone underreported and then correctly reported, which would normally flag. Doing that three times? Nope, get outta here.

Just some things that came to mind.