Helping Friend Awaken Lower Body

I was considering posting this in the beginner’s section, but what the hell. My friend is considered to be a “beast” by most. However, he has one small problem; a terrible muscle imbalance! His Squat and Deadlifts are both behind his bench. He was almost kicked out of the army for pain in his knees while running.

I noticed recently that his quads are enormous, and so is his ass, but his hamstrings are practically non-existent. He’s been squatting the wrong way for a while now. He just started trying to do it the right way, but he doesn’t have enough stability or flexibility to do it, even without weight. It’s like he’s fighting seven years of imbalanced muscle every time he squats down. It’s very odd because he really is a beast otherwise.

So far I’ve tried holding his hands and helping him squat all the way back, but I have to pull hard to stop him from falling back. He’s a big dude. So my question is this. What exercises should he be doing to correct his imbalance?

Hamstring movements. All of them.

MWOD | Feat. Kelly Starrett | MobilityWOD - YouTube you could have him put a band around behind himself right below the lower back anchored in front on the rack like at 2:15 here, also, maybe a shoe with a raised heel might be helpful - I noticed when I did some hill sprints with a friend he could sit in a squat at the top of the hill looking down (toes pointing downhill/heel higher up the hill) after he wasnt able to get down without falling backwards on flat ground.