The King of Fighters 02/03 Cheats

Defeat 40 opponents in a row in Single Attack found in the Challenge section. Rugal should be your 40th opponent.

Use any character (including the bosses) for S - Survival (One on one) to unlock the individual character portraits. For every individual you defeat in S - Survival, that individual's portrait is unlocked. Eventually, you will be forced to face Adel then Mukai separately. Defeat them to unlock their portraits and to further play S - Survival.

Use any characters (including the bosses) for T - Survival (Arcade team play style) to unlock all the team endings in the gallery. For every team you defeat in T - Survival, that team's ending is unlocked. Eventually, starting with Kusanagi, you'll fight all the bosses available in Arcade Play. Defeat Mukai during these series of fights to unlock the 3 Divine Vessels' ending (Kyo, Iori, Chizuru).

Note that the "regular" battles in both Survival games are random, meaning you don't have to unlock all in one playthrough. However, to unlock the bosses' portraits and the 3 Divine Vessels' ending, you MUST defeat a certain number of opponents.

To unlock the concept art for 2003 you must beat the Mukai path on any of the the game types Arcade, Team, or single. You can get on the Mukai path by when you get to Kusanagi beat him with a DM.