
After Hours of playing Injustice i found out how to unlock Scorpion a alternate costume. (just found him)
I cannot currently film gameplay because I do not have a video camera. Anyways, to unlock this alternate costume you must first beat Scorpions "Classic" mode. (I do not know if it works on every difficulty. I did it on Hard) then right after win 75 matches against the cpu as Scorpion. The 70th round words will appear on the screen in MK2 type font saying "You almost have it" then the match continues.
At the end of the 75th match words in mk4 font will appear saying "You are Worthy. Now Claim Your Prize!!" Then a picture of Scorpion will appear and words will be at the bottom saying "You Have Just Unlocked The Mk9 Scorpion Costume!" (The Picture seen above.) (Managed to get a quick picture of it)
You may not believe me but please just try it! It is worth it. Imagine playing online with a costume only YOU know about!