BlazBlue: Calamity Trigger

Just get a perfect round 30 times. If you wish, go into Versus and beat a 2nd controller 30 times. This can be done in any mode other than Training.

This is for getting 30 "Perfect" Rounds.
If you decide to boost for the online Rank achievements you'll get this naturally as you'll want to boost perfect rounds for more EXP.

If you don't have Xbox Live, or somehow obtained the online rank achievements without earning this one then...

The following method is the fastest:
1. Go into Options and set the number of "Versus" rounds to the maximum and set the "Versus" round time to Infinite.

2. Go into Versus mode and turn on a 2nd controller as player 2.

3. Pick Hakumen and use the Forward+B attack over and over again.

4. Repeat step 3 until the Achievement pops.

Using this method you'll complete each round in 8-10 seconds, and with a higher number rounds per match you'll minimize your loading time between rounds. You can save a few seconds by skipping the level and character intros by spamming the A button at the start of every match.