The one thing that would fully break your character.

Sparrow: Losing Rowan
Rowan: Having to go back to Black Claw
Cypher: Seeing Aerwyn relive her trauma
Aerwyn: Losing her kids or husband

Magnus: Having Nathan turn on him
Nathan: Being forced to betray his friends
Violet: Being taken back to the training grounds

Illeana: Getting found by her father

Percy: Losing Black Claw

Kinda basic but if we're talking a little more on the deeper side, ooh boy I have trauma for each of them 🎶

Nyx: losing Cade/Cade getting killed

Ella: Someone hurting Loki

Peyton: The Red Room taking her sister back.

Kai: Her son being put through the Ancient Training

Eliot: losing his business

Akos: being deported. (It makes sense in universe I swear)

Sie: being betrayed/exiled (guess what happens >:D)

Skee: letting someone get close to him only for them to use him and leave for good.

Kora: being given a terrible prophetic vision (guess what else happens >:D)

Ember: Her kids never forgiving her
Flint: Losing Rosemary
Rosemary: Someone dying under her protection/losing Flint
Flicker: Never getting answers
Echo: Getting a prophecy where someone in their family dies
Cloud: The Hollows falling apart/her kids dying/Willow dying
Willow: Watching someone she cares for deeply die

Nicole: Losing Kaylee or Maraly (she can't handle another death of someone she's close to)
Kaylee: Losing everyone she cares for
Maraly: Her adopted parents (Nicole and Kaylee) dying
Iyra: Not being able to protect her loved ones
Elijah: Watching his home fall apart
Castor: Relive his trauma/watch someone else live his trauma
Esmay: Lose Jocelynn
Jocelynn: Be betrayed by someone close to her
Violet: Watch everyone under her care die
Harper: Not being able to save someone (don't worry guys, Lea can help her)
Lea: Harper dying

Moss: Watching Glowberry, Rowan or Aspen die
Aspen: Watch her family go insane
Glowberry: Something happening to his family
Rowan: Loosing Moss (again)
Nightweaver: Seeing Brilliance win and everything she fought for crumble

This is sorted by universes lol (Forgotten Hollows first, Percy Jackson OCs after and Wings of Fire one last)

Jake: watching the universe crumble

Cassidy: being betrayed again by people who were meant to be safe

Claire: being lied to yet again.

Alex: failing others (not being able to save the people who matter to him)

Luke: losing people he is close with.