Here is the full list of all 16 Tony Hawk's Pro Skater HD achievements worth 400 gamerscore.
Completed all Projectives with one character
Got 500,000 points in one run in Venice Beach
Collected all pellets in one combo in Hawkman in The Hangar
Held a combo for 30 seconds after the time is up in Marseille
Reached the end of the Mall 3 times in a single Big Head Survival run
Completed the 100 Ski Jump gap in Downhill Jam
Scored 200,000 points without performing a single manual in one run in Warehouse
Performed 15 manuals in one combo in School II with Rodney Mullen
Won a match online
Unlocked Officer Dick
Unlocked Marseille
Unlocked Downhill Jam
Unlocked Venice Beach
Unlocked Mall
Unlocked The Hangar
Unlocked School II