The exercise performed by the first poster is called bulgarian squat. In his case he does it with dumbells, so it becomes bulgarian squat with dumbells.
Personally I have seldom done this exercise with dumbells, simply because then I would need very heavy dumbells.
I have myself done barbell lunges with 170kg for 2 reps on each leg @ approx. 100kg bodyweight.
Bulgarian Squats I have done with at least 140kg in training for reps at about the same bodyweight.
After I learned these exercises don’t help much in the squat strength (probably a bit tough), I have focused on the front squat instead (favouring it over back squats), because it feels better for mye back.
I haven’t seen anyone else do these exercises heavier than me in any of the gyms I have trained, but I guess this is not because I am so very strong, rather because other stronger atlethes don’t do these exercises.
A member of the national powerlifting team told me that lunges do for squats about what pec-decks do for benchpress. Not much in other words.
But when this is said, I have to add that bulgarian squats with a barbell on the back, doing it full ROM is some of the most brutal exercise I have ever done. If you don’t get a headache, and feel like vomitting after a gruelling set of those, then you aint doing it right. It is brutal!
To the starter of this topic: Good job on the bulgarian squats, but I think squats or front squats are a lot more impressive, that is real leg strength. When that is said, most gym rats probably could not do what you have done. So you have reason to be proud, but don’t stay satisfied for too long, it really aint that big weights!