Guitar Hero III
59 Achievements
1,000
Xbox 360
Hard Duo
Earn 5 stars on all Co-op songs on the Hard difficulty
30
How to unlock the Hard Duo achievement in Guitar Hero III - Definitive Guide
The general formula for the 5-star scores is the song for career score x 2. Use the link provided in "Shredder" for a rough view of what you'll need. Get a friend over, and 5-star everything on Hard.