"Only" 550 lbs but with a pause : Klokov Dmtry
This a Front Squat.
Venceslas Dabaya was a great front squater too (5*440 lbs):
Igor Lukanin (628 lbs) :
Mikhail Koklyaev (688 lbs) :
Julia Konovalova (418 lbs) :
etc
Front squat is a diffrent animal from back squat. It's very hard, painful but il build mobility, core strength, quads muscle mass and it's the foundation for olympic lifts.