Same thing happened to me on MK1. The moment I bought the game I tried to play it through with Scorpion and switched characters a few times but I Beat it with Sub-Zero, No Achievement. 2nd time, I just played through with Sub-Zero all the way, won and still nothing. Then I finally played with Johnny Cage, lost then chose Raiden ( i didnt really do the Test Your might challenges) and won. Once I beaten Shang Tsung and the bodies (or souls if you want to get techincal) start leaving his body, the Achievement unlocked instantly. Just thought maybe, just maybe, it unlocks with certain characters only. Just a Theory.
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