Here is the full list of all 28 Trine 3: The Artifacts of Power achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Collect each Trineangle from every Chapter
Earn every Achievement in Trine 3: The Artifacts of Power
Beat the final boss
Complete all of the main story Chapters
Collect each Trineangle from the Chapter: "The Redwood Forest"
Complete the Chapter: "The Redwood Forest"
Collect each Trineangle from the Chapter: "The Chronicles of the Guardian"
Survive through the Chapter: "A Whisper of Evil"
Complete the Chapter: "The Chronicles of the Guardian"
Complete the Chapter: "A Wizard's Epiphany"
Survive through the Chapter: "A Dangerous Outing"
Complete the Chapter: "A Wizard's Nightmare"
Collect each Trineangle from the Chapter: "The Astral Academy"
Complete the Chapter: "The Astral Academy"
Complete the Chapter: "A Brush with Death"
Survive through the Chapter: "An Academic Invasion"
Complete the Chapter: "A Lonely Knight"
Collect each Trineangle from the Chapter: "Academy Outskirts"
Complete the Chapter "Academy Outskirts"
Complete the Chapter: "A Forgotten Parchment"
Survive through the Chapter: "A Squabble in the Jungle"
Complete the Chapter: "A Tumble Down"
Collect each Trineangle from the Chapter: "The Three Heroes - Amadeus"
Complete the Chapter: "The Three Heroes - Amadeus"
Complete the Chapter: "The Three Heroes - Zoya"
Collect each Trineangle from the Chapter: "The Three Heroes - Zoya"
Collect each Trineangle from the Chapter: "The Three Heroes - Pontius"
Complete the Chapter: "The Three Heroes - Pontius"