To earn this achievement you must defeat Noob Saibot, one of Shao Kahn's deadliest warriors and the former Sub-Zero. Noob Saibot is a very difficult fighter to beat, but there are a few ways to do this:
1- You get a chance to fight Noob Saibot once you beat the arcade mode with any character. After you defeat Shao Kahn, you will be asked to choose a prize. These take the form of various symbols. To fight against Noob Saibot, you MUST select the the fourth icon from the left which appears to be a 3. This will trigger a 2 round fight with Noob Saibot, win this fight and the achievement is yours.
2- If you have a second controller, instead of going to arcade mode and selecting the Mortal Kombat option on the left, choose the third option, 8 player tournament, at the far right. Tournaments consists of a dozen LOCAL (using 2 controllers only) single round fights between 8 players to determine which of the 8 warriors will prove to be the strongest. However, the winner of tournament gets to choose a prize identical to the ones from the arcade mode. Once again, select the fourth icon from the left, the one with a 3.
TRICK- If you cannot defeat Noob Saibot, try this. Start-up a 8 player tournament with 2 controllers. On the character select screen, using both controllers, choose Liu Kang for all 8 players. It doesn't matter who wins in the tournament JUST MAKE SURE THAT THE WINNER IS ONE OF THE FIGHTERS CHOSEN BY THE PRIMARY PLAYER'S CONTROLLER, after all you are the one that wants the achievement, right? Once the tournament is over, select the fourth icon from the left, the 3. When the battle starts, using Liu Kang, do not move. Instead just tap the A button (low punch) over and over. Sooner or later Noob Saibot will try to sweep your character's legs, since you are tapping A, Noob will get stuck and continue to try to sweep. Instead, you will punch him the head until he loses all of his health and you will win the round. Repeat the exact same method as before in round 2 and there you go! You have beaten the Noob!
In the occasion that he breaks the sweep cycle and you lose a round or the match, keep trying. I am not a great Ultimate Mortal Kombat 3 player, yet this has always worked on my profile and various friend profiles.
If you wish to truly fight Noob Saibot you will need quite a bit of skill.
-Noob Saibot will recognize patterns quickly. This makes it impossible to spam Scorpion's spear move or Smoke's Uppercut, Spear to combo move without getting killed.
-Noob Saibot's stage is very dark and because he has is wearing a pitch black ninja suit, he is sometimes very hard to see.
-Noob Saibot has ultra powerful special shadow moves. He always knows when to use them and they will prove to be very cheap sometimes.
-Noob Saibot has a very aggressive fighting style. Expect him to try to steamroll you as soon as the announcer says FIGHT!
-Noob Saibot sometimes jumps quite a bit during rounds, use it to time damage dealing uppercuts.
Learn your character and mix up the attacks, expect him to bounce everywhere on the screen and try to make out his pattern. Aside from that, I cannot transfer luck or skill so be patient and keep going!
YOU CANNOT PLAY AS NOOB SAIBOT. Just so you know.
If there is anything I am missing or if there is something that you do not understand, please, leave a comment and I will be sure to change the solution accordingly.
FIGHT!