There are 300 challenges on the tower.
Here are some of the more difficult ones:
Baraka vs Sheeva, Goro, Kintaro
Shang Tsung vs Shao Kahn
Shang Tsung vs Baraka, Sindel, and Shao Kahn
Stryker vs Shao Kahn, Shao Kahn, Shao Kahn
Ermac vs Goro, Goro, Goro
End Game: Character of your choice vs Goro, Kintaro, Mileena, Shao Kahn
The key to beating End Game (challenge #300) was sticking with it. Don't keep retrying. Play until you die and then retry. If you do that, after about 5 or so fights, you will start to regain health back after you beat a fighter. I eventually was getting about 1/3 of my health back after each fight and that is what helped me beat it finally. I'm not sure if that is true for any of the others as I didn't find that trick until #300, but it is worth trying.
Here are some of the more difficult ones:
Baraka vs Sheeva, Goro, Kintaro
Shang Tsung vs Shao Kahn
Shang Tsung vs Baraka, Sindel, and Shao Kahn
Stryker vs Shao Kahn, Shao Kahn, Shao Kahn
Ermac vs Goro, Goro, Goro
End Game: Character of your choice vs Goro, Kintaro, Mileena, Shao Kahn
The key to beating End Game (challenge #300) was sticking with it. Don't keep retrying. Play until you die and then retry. If you do that, after about 5 or so fights, you will start to regain health back after you beat a fighter. I eventually was getting about 1/3 of my health back after each fight and that is what helped me beat it finally. I'm not sure if that is true for any of the others as I didn't find that trick until #300, but it is worth trying.