Here is the full list of all 12 South Park Let's Go Tower Defense Play! achievements worth 200 gamerscore.
Activate a Special Ability
Earn a Gold, Silver or Bronze Medal on any level
Watch a video clip in the Scrapbook
Destroy an enemy with the junkyard crane near Kenny's House
Collect 100 coins in 10 seconds or less
Save South Park
Collect 1,000 coins
Throw 1,000 snowballs
Earn a Myrrh Medal on any level
Earn a Platinum Medal on any level
Earn a Bronze Medal or better on 5 Challenge levels
Beat Mountain on Insane difficulty using walls and snowballs. No towers!