This is without a doubt, the hardest stage in the game. At least it was for me. The enemy that chases you requires either extreme timing (to kill him), or luck (to have him just decide to disappear).
@ManekiNeko1972 About 3 1/2 - 3 3/4 door lengths away when he's at a full run. Also, you'll need to be moving in the opposite direction when you hit the lever, or else he will end up hitting you still while dying. I find on level 7-1, the easiest spot is the first shutter, as it's pretty much a full speed run to the lever once you stun him with the door, then just let go of the analog stick, and then just hit up.
I am curious that how you could make the giant go in that black door at 7:08 and how you manage to use one shot to kill the two guys at 7:20. These are the difficulties that prevent me from obtaining the gold medal in that stage. The two guys are especially annoying. I can only shot the guy in the back. The front one is hard to deal with if the giant does not go into the black door.
