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