According to OP (translated from spanish to english):
"Hi, it's Xnorverse89 here. Thanks a lot for playing KOF Theory Mercenary
I hope you enjoy it to the fullest.

This version of KOF Theory Mercenary features far more characters than previous releases. They are better, more epic, more overpowered, and stronger—I guarantee you're going to love it. That said, I did have to remove a few characters and stages because they would occasionally glitch, crash, or stop working, though this happened very rarely."