Here is the full list of all 12 Pac-Man Championship Edition achievements worth 200 gamerscore.
Complete Extra Mode 3!
Eat the Crown!
Complete Extra Mode 2!
Complete Extra Mode 1!
Eat the Key!
Score 200,000 points!
Complete Championship Mode!
Eat 8 ghosts in succession!
Emit sparks for 1 second!
Score 400,000 points!
Complete Challenge Mode 1!
Complete Challenge Mode 2!