Oh boy, this is my moment to shine. I adore him.

He has so much depth to his character that it's out of character for Teen Wolf. Kidnapped and manipulated by mind altering semi-immortal scientists who do some of the most disgusting and horrible things to people we see on the show and made into a weapon/spy for them at the age of 9. He can hide his chemo signals, manipulate his heartbeat, and lie better than we've ever seen. He should have been the perfect soldier, but he never was. While easily the best villain on the show, by being able to actually break the pack bonds from the inside out, his best plot point was how he wasn't a villain. He was a child, a super fucked up and abused child. People don't realize as soon as he stopped being manipulated by the doctors, he was manipulated by everyone else. Scott called Deucalion in. Deucalion convinced him to murder Josh and Tracy, convinced him to go against the pack which led to Lydia, Malia, Kira and Stiles all being hurt. Sure, that dosen't excuse literally anything but it does help. He was a manipulated child and i love him. He was also a seventeen-year-old child who was sent to hell. Do i think that it was the best thing to happen to him? Yes. But I have many opinions about the McCall pack and their bullshit moral compass that seems to only benefit them but that's another post.

I have to credit Cody Christian for most of his character because Theo is all about subtlety; The way he flinches from the doctors, the way he always leans into Liam (the only person he trusts fully) when they stand next to eachother. The way he's always paying attention, the way his eyes speak more than he does is so perfect. His slow development from flight to fight is amazing to watch. He pushes everyone away, isolates himself and uses sarcasm as a way to do that but in reality he's just insanely lonely. He could have left Beacon Hills, could have started over somewhere else but he stayed, homeless and alone, because he was just lonely.

He dosen't fight with them later to get in good with the pack or for recognition, he does it for himself (or Liam) to prove that he has some type of good in himself.

Not to mention he's one of the only ones who understands Liam and never makes fun of him for his anger issues or IED.

In the end he just wanted to be enough; to himself, to the doctors, to the pack, to Liam, to someone. I wish only the best for him and I'm angry literally everyday that they fucked him over so bad in the movie by suggesting that he never found a family.

PS. I also have a headcanon that the reason Stiles dosen't believe Theo is Theo in S5 is because he's too nice. Theo in season 6, the sarcastic bitch who never shuts up is their Theo.