PATIENCE is key, be prepared to see a lot of loading screens.
99 seconds (Extremely beneficial, DO NOT pick 30 seconds or even 60, if you do you may need to replace your controller(s))
Bonus Stages OFF
Match Request OFF
Pick your best character, or Zangief. I personally used Zangief because I'm shameless when fighting CPUs. Although it's hard to resist pile-driving your opponents over and over the amount of damage to the amount of time spent in the animation makes it very inefficient for this achievement; the reason you would want to use Zangief is purely for Lariat abuse against the CPU; Flying Body Press (optional) -> Lariat -> Lariat -> Lariat etc. all the way through arcade will eventually get you a quick win against any and all opponents, especially Seth.
The most important thing to know when going for this achievement is that it's OK to lose a round and continue! If you fail to pummel your opponent before the 78 second mark (finishing with 79 seconds left is the absolute latest you can win a match to remain eligible) just keeping walking straight into the CPU and let them finish you off, pick your character again and keep going at it. If you pick any amount of time LESS than 99 you're not doing yourself any favors, should you fail to kill your opponent in less than 20 seconds one of the rounds you will want to to give as much time as possible to the CPU to poke you to death, especially if you're using a character with high vitality such as Zangief. The last thing you want to do is accidentally win by time running out.
It may take many tries for any CPU to co-operate and you may have to waste precious seconds of time blocking/avoiding ultra maneuvers but unless your opponent is stunned always use caution when approaching them or attacking after they sustain enough damage to unleash an ultra because the amount of time it would take for the animation to finish and for you to reposition yourself is always longer than it would take to just sit back and block/avoid it. Obviously, prior experience will help greatly in knowing exactly what you need to look out for, for example if you're fighting Ryu or Dhalsim with their U1 and you're Lariat spamming just keep at it relentlessly, you should have no worries considering you'll spin right through their projectile and land another hit on them.
If you get your opponent very near death and with only a second left to spare don't panic and just do yourself a favor, throw the match in their favor and try again. If you ended up accidentally chipping an opponent even a second late you'd effectively nullify your eligibility for the achievement and you'd have to do everything over again.
Also, although I don't recommend it and it isn't necessary you can switch characters after continuing at will and still get the achievement. The only practical use is if you're having trouble beating a particular character in time (such as T. Hawk and his massive vitality gauge) you can switch characters, lose, then switch back to your original choice and you should be facing an entirely different person while still maintaining your wins/time up to that point.
If you've got the patience it's a very simple achievement to get, happy hunting.