Full list of all 45 Skylanders Giants achievements worth 1,000 gamerscore. It takes around 25-30 hours to unlock all of the achievements on Xbox 360.
Complete the Story Mode on Nightmare difficulty
Amass 65,000 Treasure with any one Skylander
Complete all 21 Arena Challenges
Purchase all upgrades for any one Skylander
Complete Chapter 13
Complete Chapter 14
Complete Chapter 15
Complete the Story Mode by recovering the Iron Fist of Arkus and defeating Kaos on any difficulty
Chapter 13 - Destroy all the columns in the second trial
Chapter 14 - Collect all 16 speed boosts in "The Long Hall" section
Chapter 15 - Defeat Freebot in a game of Skystones
Chapter 16 - Complete the chapter without taking damage from fire traps
Don’t take any damage from Kaos' rockets during the mini-game on the Dread-Yacht
Collect soul gems for Tree Rex and Jet-Vac
Complete Chapter 12
Chapter 12 - Destroy 3 enemy huts with boulders Giants can lift
Collect 10 Legendary Ship Parts
Collect 10 Story Scrolls
Complete Chapter 11
Chapter 11 - Damage Drill-X by throwing a pipe at him
Level up any Skylander to level 15
Complete Chapter 10
Chapter 10 - Shoot down 10 mines
Complete Chapter 9
Chapter 9 - Destroy 10 Kaos Bust Statues
Complete Chapter 8
Chapter 8 - Complete the level without getting directly hit by a cannon
Chapter 7 - Talk to all of the Wilikins
Chapter 6 - Destroy all the Arkeyan Autogyros
Complete Chapter 7
SkyStones - Capture 2 stones with 1 single stone
Complete Chapter 6
Collect 10 Hats
Complete Chapter 5
Chapter 5 - Destroy 7 snowmen
Earn 3 Stars on any Adventure Level
Complete Chapter 4
Chapter 4 - Collect all of the Skystones
Complete your first arena challenge
Complete 1 Heroic Challenge
Complete Chapter 3
Chapter 3 - Complete the Log Lift Feat of Strength
Chapter 2 - Complete the Chain Pull Feat of Strength
Chapter 1 - Open all the Elemental areas
Unlock your first Elemental area