Set the difficulty to "Ultra Hard", the time to "Infinite", and the life bars (1P game) to "Infinite". You can now easily get the "Noble Soul" achievement without worrying about losing. Note: The only way to win is by getting your opponent out of the ring. Try using Seung Mina's kick. Also, use caution when fighting characters such as Astroth and Taki. Taki tends to block a lot and Astroth has a lot of powerful moves, most of which push you off the stage.
Amy's ending seems exactly like Raphael's until she walks up behind him and elbows him into the pit. Although it is a different ending cinematic, the announcer says "Ring Out", just like if it was a match.
ACHIEVEMENT - HOW TO UNLOCK Apprentice (5 points) - Play 3 characters in any mode. Warrior (10 points) - Beat Arcade Mode. Zen Warrior (10 points) - Win a round with a perfect. Noble Soul (25 points) - Beat the game in Ultra Hard without losing a round. Champion (25 points) - Beat Time Attack Mode in under 4 minutes. Ring Out (15 points) - Finish Time Attack Mode with all Ring Outs. Conqueror (25 points) - Beat 25 opponents in Extra Survival Mode. Close Call (15 points) - Defeat an opponent under adverse conditions. Guardian (15 points) - Perform 25 consecutive bursts with Freestyle set to Guard Impact in Practice Mode. Art Connoisseur (5 points) - Explore the different areas in the Museum. Summon Suffering (20 points) - Perform the move Summon Suffering with Ivy. Edge Master (30 points) - Beat Arcade Mode with all characters.