Here is the full list of all 46 Skylanders Giants trophies - there are 36 bronze, 6 silver, 3 gold and 1 platinum.
Earn all other Trophies
Complete the Story Mode on Nightmare difficulty
Amass 65,000 Treasure with any one Skylander
Chapter 15 - Defeat Freebot in a game of Skystones
Complete the Story Mode by recovering the Iron Fist of Arkus and defeating Kaos on any difficulty
Chapter 16 - Complete the chapter without taking damage from fire traps
Complete Chapter 15
Complete all 21 Arena Challenges
Chapter 14 - Collect all 16 speed boosts in "The Long Haul" section
Chapter 12 - Destroy 3 enemy huts with boulders Giants can lift
Chapter 11 - Damage Drill-X by throwing a pipe at him
Complete Chapter 14
Collect soul gems for Tree Rex and Jet-Vac
Complete Chapter 13
Chapter 13 - Destroy all the columns in the second trial
Complete Chapter 12
Complete Chapter 11
Chapter 7 - Talk to all of the Wilikins
Collect 10 Legendary Ship Parts
Complete Chapter 10
Collect 10 Story Scrolls
Chapter 10 - Shoot down 10 mines
Complete Chapter 9
Chapter 9 - Destroy 10 Kaos Bust Statues
Purchase all upgrades for any one Skylander
Level up any Skylander to level 15
Chapter 8 - Complete the level without getting directly hit by a cannon
Chapter 6 - Destroy all the Arkeyan Autogyros
Chapter 4 - Collect all of the Skystones
Don’t take any damage from Kaos' rockets during the mini-game on the Dread-Yacht
Complete 1 Heroic Challenge
Earn 3 Stars on any Adventure Level
Chapter 1 - Open all the Elemental areas
Complete Chapter 8
Complete Chapter 7
Complete Chapter 6
Complete your first arena challenge
Complete Chapter 5
Chapter 5 - Destroy 7 snowmen
Complete Chapter 4
SkyStones - Capture 2 stones with 1 single stone
Collect 10 Hats
Complete Chapter 3
Chapter 3 - Complete the Log Lift Feat of Strength
Chapter 2 - Complete the Chain Pull Feat of Strength
Unlock your first Elemental area