This is literally all the mc's fault. She couldn't told him she wanted to conquer the labyrinth with him instead of using him, traumatizing him and throwing him away. It was weird for her to test him only to throw him away afterwards. If this was written in his pov and he got his revenge by killing her, it would've been justified. He doesn't know why she did what she did. He simply was forced to fight and go on impossible mission, and suffer without understanding why. Then she even took his one purpose in life and decided she was going to do it without him. Even though that was his entire goal. It was cruel, it wasn't well thought out and any hostility he has towards her is justified. She was being dumb as he** when it came to him.