In order to get this achievement, you must play through ladder mode, never losing a round until you reach Shang Tsung. Once you reach Shang, you must win with a double flawless and then a fatality. However, you must also not lose a round to Shang Tsung, which means you cannot quit out to the character select screen right after you take a hit. To make this easier, if you get hit, play through the match, still without losing a round, until you get to "Finish Him." Once you're able to finish him, then you can quit out to the character select screen because the game will have considered you to be the victor, but you won't be able to move on to the next fight until you deliver the finishing blow.