This is really HARD! Here is the help provided by PowerPyx:
- Set the amount of rounds to 2 in options
- Start a new ladder in Beginner (pick Scorpion)
- Do NOT lose any round until reaching Shang Tsung
- Note that it is NOT necessary to do a fatality to ALL fighters!
- You have to perform TWO flawless victories in a row vs Shang Tsung
- This can be done with ANY fighter
- When you beat him you have to perform a Fatality
- After a loading screen Jade will appear and also the trophy.
One Tip here: If Shang Tsung hits you, you DO NOT need to start the ladder all over again; just win the match and when the "Finish him" label appears don't perform it, pause the game and select retry OR change fighter. Doing that DOESN'T count as a loss and you will be able to try and get a double flawless again!
Thanks to PowerPyx for the video: