Here is the full list of all 43 TRI: Of Friendship and Madness achievements.
Reflected one single light ray 50 times.
Complete TRI.
Find all hidden idols in 14 levels.
Play through Chapter 14 and 15.
Find one of the two super secret idols in "Out of Space and Time".
Find one of the two super secret idols in "Prisons".
Play through Chapter 12 and 13.
Find the super secret idol in "Going Astray".
Laser yourself to death ten times.
Find the super secret idol in "Out of the Box".
Play through Chapter 9 to 11.
Find one of the two super secret idols in "Red Means Dangerous".
Find one of the two super secret idols in "Interrupting and Bending".
Fall into deadly acid pits ten times.
Find one of the two super secret idols in "Glimpse of Light".
Play through Chapter 5 to 8.
Find all hidden idols in seven levels.
Find the super secret idol in "Wings in the Void".
Create 1,000 triangles.
Find one of the two super secret idols in "Unwilling Walls".
Beat "Overcoming Limitations" without collecting the TRI artifact.
Find one of the two super secret idols in "The Foxes' Playground".
Create the biggest triangle possible.
Find one of the two super secret idols in "The Odd Gods' Entrance".
Find all hidden idols in three levels.
Find one of the three super secret idols in "Overcoming Limitations".
Play through the first four Chapters.
Find one of the two super secret idols in "Three Sides to Everything".
Find all hidden idols in one level.
Find one of the two super secret idols in "Tower of Nowhere".
Play through the tutorial mission.