In the Phazes circuit #8 there are these brutal exercises called pistol squats. My trainers show options of a single leg squat going to the ground unassisted or just holding onto a chair. I took the easiest modification and it was still hard! But I could not even do this much 2 years ago. 10 years ago I was doing pistol squats without the chair support. Try single leg pistol squats with a leg out in front and tell me how it goes for you.