Instructions
Choose your character from the roster. Each character has a different move combo for their Friendship and you will want to practice the combo before attempting. You can find a move list through a quick search online.
Win the first round of the fight with any method including special attacks, blocking, repeat kicking, etc. In the second round however, you must not use block.
Defeat your opponent in the second round (without using block) and enter your character's move combo when "Finish Him" appears on screen. For instance, to perform Kitana's Friendship you would enter: down, back, forward, forward, low punch.