“Xena: Warrior Princess”

Rachel’s true love was the war, she feel head over heels in love with the battle. Her only fear was her realisation of what her blood lust was doing to her soul. At the end of the series her mother called her out on it, describing her own daughter as a monster.
Rachel was terrified of what she was becoming, but still didnt turn away from it, she needed the fight and war like a drug, and at atleast one point each of the characters mention how they are worried about what will happen to her after the war ends.

“I don’t think anyone really understands where you’re coming from Rachel.  You’re too into it and for a while we were all right with that.  But now it’s kind of starting to freak everyone out.” ~Tobias #48

Tobias loving her (and her love for him) was the only thing keeping her grounded and he constantly had to keep reminding her of who she really was so she didnt loose herself in the violence forever.

Helping to protect their innocence… …They needed me to be the bad guy. And I needed them to be the good guys. See, if they were good guys, and I was on their team, then that automatically made me a good guy, too. Even if I was different. ~ Rachel, #48

Jake picked up on her blood lust pretty early and started using it to his advantage

“I think your the bravest member of the group.  I think in a bad fight I’d rather have you with me than anyone else.  But yeah, Rachel, I think there’s something pretty dark down inside of you.  I think you’re the only one of us who would be disapointed if all this ended tomorrow…  …But you, Rachel, you LOVE it.  It is what makes you so dangerous to the yeerks” ~Jake #22

So, in the final battle, like his dog on a leash he let Rachel loose and sent her on a suicide mission. He knew it would win them the war. They both knew she wouldn’t be coming back alive, she only hesitated to make sure Jake understood, and told him not to blame himself. She then went, without anyone else knowing, because she knew if anyone else knew they would either try and stop her and that would mean game over, or they wouldn’t and that would eat them alive forever. She took off alone, on a warriors final hunt, achieved her goal and killed her cousin, and then was killed in battle.

“you fight well, human” ~ yeerk who ended her life, #54

Despite this, despite the war being her life and love.  Rachel chose in her final moments not to fight.  She chose to spend her last minute alive to look into the eyes of a boy whose humanity died with her, to tell him she loved him.

“Yes, you were brave. You were strong. You were good. You mattered” ~ Ellimist, #54

During the series, she earns the nickname:
Rachel of the Dark Heart.