Generator Rex: Agent of Providence

Before you attempt this, select the last level (Abysus), play for a while and see if the timer disappears completely. If it disappears, this usually means the glitch happens and when you finish the level, the timer will be at 00:00:00 and the achievement unlocks without trying. This is quite nice glitch, since this is arguably the hardest achievement in the game.

I found this achievement to be easiest to obtain on Aquania. I will give you times so that you are aware of just where you need to be when.

It took me 41 seconds to get through the first door that you see when you're jumping.

Using the funchucks, I was able to defeat Biowulf by 2:33. Use the gun to blow open the door you have to continue through, and once you get half way in you can shoot the eye as soon as the yellow targeting reticule appears. When you finish the next area and have to go up to the top to shoot the eye, you don't have to go all the way up. You can shoot the eye from about half way down and then run back while the cutscene is going.

I made it to the boat at 5:24. When you get to the end of this jumping area, don't go inside or use your fists. Shoot the door and then shoot the eye all from outside.

Got to the final boss at 6:27. At this point, once I ran inside I found that you can skip past the forced walking part by selecting restart as soon as you are actually inside and fighting the boss. Once you select restart, keep the thumbstick moving in the right direction because you can run before you can actually see what you're doing. This will save you 10 seconds.

Actually defeated the boss at 9:25. This part is super important, because there are an extra 30 seconds of cutscene. At one point on a previous run, I managed to defeat the boss and the screen went black at 9:57. Woo achievement!!! No, apparently the counter keeps going after that until 10:05. Shenanigans!!!

Hope this helps. My general strategy for fighting things is to use the fists. With the heavy attack and the "tap y to extend' upgrade you can fill up your omega meter by doing an extended heavy attack on two guys if it's fully drained. Use the axes any time you have four guys surrounding you OR any time you see a red crab. These ones take longer to kill so it's better to just slice them up. Make sure you save one guy to top off your omega meter for the next battle. When you reach the areas with the spawning hole things, don't kill anybody. The first thing you should do is run up and use a quick spin of your bad axes to destroy the spawning pits so you don't have to fight more than one person from each.

You might also be able to get this achievement in Hong Kong. I managed to get down to 10:19 but decided to try for this achievement in Aquania instead because I wasn't sure if it was possible to shave any time off in Hong Kong. If you're having trouble in Aquania, you might try there.

best mission for this is the Aquania mission when going for the time trial - the target time is 12 mins so to get under 10 isnt too bad. To help you along i recommend using the omega whip on the biowulf and octobrain thingy bob (krang lookalike from turtles) as it deals massive damage making the fights go much quicker. Also to note you need to leave yourself a buffer of 20 seconds or so as theres some bullshit cutscene at the end of the level that the timer still sounts for some god forsaken reason.