Kaidan's backstory is underrated and more interesting than you think
People that decided to save Ash on Virmire tend to say that Kaidan is boring, his story is bland and he has no personality but this can't be further from the truth.
First of all I don't invalidate your personal preferences for Ash over Kaidan, it's your decission. And now let's talk about why Kaidan's story is actually good and why he seems boring for others.
Kaidan's story is about physical child abuse. A bunch of kids that were forced to exposed to unknown element that could be potentionally dangerous and cancerogenic just to experiment on them. They were beaten, forced to train till total body exhaustion, it was physically and emtioally extremelly hard, they were abused physically and emotionally just for an experiment with something they weren't even sure how it actually works. This type of treatment leaves big traumas and PTSD in people, especially if they are kids or young adults with their brain still developing. It was very unprofesional, dangerous and unethical to install experimental chip to brain in middle ot developement.
The story of Kaidan is similar to Jack's story. They were both physically and emotionally abused for biotic powers. The main difference is how each of them dealt with trauma differently. They were both deeply damaged for life - it made Jack a sociopath and Kaidan was left broken and empy. Jack is full of anger, she wan't to give others the pain she suffered, Kaidan is actually depressed and don't wan't inflict the same pain on others - two sides of the same coin... of trauma.
I love Kaidan, I don't think he is dull character at all and I wish more people saw the psychology behind him as I do.
For me personally this is way more interesting than high school drama from Ashley, but it's just a personal opinion.
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Please not that I'm not a professional psychologist or psychiatrist however I'm a medical student and I've read a lot about mental health issues. If you are a professional let me know where and why I’m wrong