After beating the Story and Guardian mode and obtaining most of the Achievements in the process, I believe that many of the "bugs" related to achievements that people are running into (myself included) are simply a result of the achievements being worded in a confusing/misleading manner. I suspect this may have resulted from improper English localization of the game when it was being translated from the original Japanese.
In any case, you might be able to avoid significant confusion by updating the following achievements to more accurately describe their requirements: (Achievement
- Current Text :: Example Updated Text)
- Vengeful Tidal Wave of Fists - 100 combos completed. :: Execute a 100-hit combo.
- The 'Knock Your Teeth Out' Fairy - 300 combos completed. :: Execute a 300-hit combo.
- I'm Gonna Punch You 'Til You Cry - 999 combos completed. :: Execute a 999-hit combo.
- Hat-trick - Bounce an enemy 3 times in the air without it touching the ground. ::
Bounce an enemy off of other enemies 3 times without it touching the ground.
- Quadruple Axle - Bounce an enemy 4 times in the air without it touching the ground. :: Bounce an enemy off of other enemies 4 times without it touching the ground.
- Endless Waltz - Bounce an enemy 7 times in the air without it touching the ground. :: Bounce an enemy off of other enemies 7 times without it touching the ground.
There are probably even better ways to phrase the requirements (please chime in below if you have thoughts on the matter), but I thought I'd put this list up just in case other people are looking through the forum wondering why a particular achievement doesn't seem to be unlocking.
As a side note, the same localization issues apply to some of the skill descriptions: Direct Volley's damage boost is a function of bouncing an enemy off other enemies, not just keeping it airborne. This is an excellent game, but I think players can potentially be put off by the inability to understand certain aspects due to description errors.