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.
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
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.