You must play as Kotal Kahn using any variation. There is a special attack called "Blood Offering". It takes away 10% of your health, but increases your damage output for a short period of time. You must use this move to kill yourself when your health is below 10% (Right, Down, Left, Circle). Start a match on the Very Easy difficulty. Let the enemy attack you until your health is really low, and then kill yourself with the Blood Offering special attack. Make sure not to use this special attack too early, as it has a long cooldown time. Then, simply win the match to get the "Hara Kiri" trophy.