Pretty easy achievement, I got this unlocked in under 5 minutes.
If you know nothing at all about this game, you may have a bit of trouble, but this is pretty easy.
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1. From the Main Menu go to MISSION
2. Go down and select SURVIVAL
3. Select the default character that you start on (KYO)
4. Defeat 3 characters and the achievement will pop as soon as the 3rd fight is over
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If you are having trouble, try playing ARCADE mode to get the hang of things. Using dash movements is very useful. (Quickly press Left or Right twice on the Analog Stick/D-Pad)
Mash some buttons and you'll get this.