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