Fionnmac-A little bit on your knees at the bottom, tri to keep over the midfoot/heels. Practice air squats shoving the knees out hard with your toes curled up from the floor in your shoe will give you the feel for it. Try squatting with your feet an inch or two from a wall without falling over backwards helps as well.
A little bit short of depth but getting close to parallel now. Not enough hip drive. You are still doing a little bit of a leg press with bar on your back. Practice the drill where your mate puts his hand on your lower back at the bottom position and forcefully drive it up. Bar position isn't quite right. Needs to be a bit lower than that. That is probably why it hurts you haven't quite found the groove yet. Try placing your hands a bit wider.
http://squatrx.blogspot.com/2009/01/...squatting.html
Small pictures but this demonstrates the difference in position between high bar and low bar.
Unknown solider-Getting there. Improvement for sure. Your main issues are right at the bottom of the descent where you are having trouble with the position. You are slowing way down at the bottom and not quite getting the depth or a decent stretch reflex. Knees out harder should give you the room to get that extra depth and take advantage of the stretch reflex. Also it will allow you to descend into position a tad more quickly at the bottom. Also lacking hip drive.
Check the OP of this thread think it has an awesome vid of Malanichev demonstrating hip drive.