I got this achievement in less than 5 minutes with the following method:
* practice mode -- choose Sabrewulf
Stand next to your opponent and rotate the thumbstick while spamming
*If facing right, rotate clockwise.
*If facing left, rotate counterclockwise.
This cranks out tons of 8, 9, 10, and 11-hit combos. You'll find it works most efficiently when you have your opponent pinned against the edge of the arena.