Great guide. It helped me a lot to get this achievement which I think is the hardest out of both Watchmen games. Here's some things I'd like everyone to know.
Pausing is allowed. I can 100% say this as I paused and took about a 30 minute break and came back to finish the game to unlock the achievment.
I don't know if doing finishing moves really hurt your time that much, I say this because for the first 3 levels I was using a bunch of finishing moves and then I read this post and from the op suggestion, I stopped using the finishers. When I beat the game, I was overtime by 2:30, but to my surprise, the achievement popped. I don't know why, but I can assume that maybe when you do the finishing moves, it slows down the clock as your fighting becomes slowmo when you pull off a finisher. Thoughts??
As far as the bathroom scene on the first level, Here's what happened to me. I ran in, beat up a few guys, then the explosion happened. I then thought to myself, "Run to the end of the level." I ran to the end, but it did not end the level, I thought "crap! I gotta backtrack now." But when I turned around there was one enemy right behind me, I beat him up and the level ended.
I did not think I was going to be getting this achievement on the 1st try, but I did. I was running way way behind schedule and I lost a lot of time on the sewers. By the time I was at the final boss, I only had 6 or 7 minutes to do it in, I thought I was screwed, but I went through it anyways.
Tips I'd like to add:
*Just keep going even if you think you are running long on time, you might be surprised and unlock the achievment anyway.
*don't have to use finisher combos. I never figured out how to use them properly, I just used YYY most of the time.
*If you are only down to 1 or 2 guys from a group, but they just keep countering your attacks (very annoying) and you are loosing a lot of health, use your charge to save you even if it means using it with only 2 guys around. You don't want to risk dying. Stay alive at all costs.
*When fighting Underboss at the top of the tower with the pipes he jumps to, after he uses the flame thower once and enemies start appearing, you throw an enemy to knock Underboss off the pipes, beat up Underboss, but keep some enemies around if possible. Once he jumps back to the pipes, immediately grab an enemy and throw him at the pipes. Do this before Underboss can even use his flame thrower. Keep repeating this till he's dead. You'll save a lot of time and he'll never get a chance to use his flame thrower on you again, he will only use it the first time.
I hope my extra tips help anyone reading this. This is probably the most annoying achievement I've done in a while, but it is definately doable. Just know where you need to be going and run, run, run to the next group of baddies to beat up. Thanks to the Op of this thread. You helped me to get this achievment and for that I am grateful.