"But Zita," I imagine someone could say, "why do you claim to love Cortana so much if you talk about how ruthless/toxic she was?"
Because I think it's awesome, that's why.
I love that Cortana wasn't okay. I love that Cortana was a weapon with no future she could claim for herself and a seven year lifespan. That she was meant to spend that handful of years hunting and killing for the masters that would discard her when it expired.
I love that with time, her loyalty to those masters broke down and rebuilt itself around the one person who was kindest to her.
I love that a creature like Cortana did not know how to love someone, that she did not have the time to learn to approach with care and to hold without crushing in her grip. That her sincerest feelings were terrifying to behold. That the harder she tried to protect the person she loved most, the more damage she did to that one friendship that had sustained her when all else failed.
She was so beautiful and so tragic and I love her.