This achievement is story-related and can't be missed.
It will unlock after beating Stage 7 on normal or casual mode on your first playthrough.
This is an easy fight if you understand the patterns and react quickly.
Here's what you should do:
- Using Zangetsu or Miriam, crouch and wait for the first attack;
- Jump over the blue block highlighted that is next to the boss and hit him 2 to 4 times;
- When he grabs on the sides of the room, move to the blue block that is not red-targeted, hitting the boss if possible;
- Wait on top of this block until the block in which you stand is red-targeted;
- Jump down quickly and position yourself on the floor facing the block where you came from e close to it;
- Crouch and spam regular attack
until blue blocks highlight again;
After you land the last hit, boss will give you his last blow. Blue blocks will shine again, but this time stay on top of the upper center one and drop down as soon as it becomes red-targeted.
Please refer to this video by YouTube user DenSetsu for the complete fight: