There are three secret achievements for a total of 40 additional gamer points in Thor: God of Thunder for the Xbox 360.
Check out my other guide if you’re looking for the full list of achievements.
Ejected (5 points) – Rip the J’tun warrior out of the Frost Goliath’s chest
Gentle Giant (10 points) – Spare a Mire Giant
Homecoming King (25 points) – Defeat Mangog