“Our flesh will pierce their steel” was a quote stuck in my mind, i couldn’t help but link it to black knight trading her humanity for immortality. Thus Rex is more human than she’ll ever be despite not being human in the first place.
In episode 3, when Six says "In our line of work, we need to be careful. People we pull into this life, they can too easily get caught in the crossfire."
And that always stood out to me bc it feels pretty personal, but we don't actually know who he's talking about. Not Holiday - she was in Providence before they met. Not One, he brought Six willingly into the life, and people don't really turn due to exposure with EVOs, so Six wouldn't have "pulled" him into anything. Maybe White getting bleached, but that was more a result of his own actions.
I always kind of thought it was a character we never met, an ambigous "someone" that died in his past, but on a rewatch today, it clicked that while Rex was talking about Circe...Six was talking about Rex.
Six brought Rex to Providence when he could've brought him anywhere else. Providence would've believed the robot destroyed - they did believe the robot was destroyed. Thry definitwly had no reason to link it to this kid. But Six brought this child, this EVO, to a place where he had earlier that day watched them kill another EVOfor research, where they had other human EVOs explicitly caged to deconstruct. He took Rex into the lion's den to show Holiday, and Rex had no idea. Six could've been more careful, and taken Holiday to see Rex instead.
But he was emotional. He was tired from seeing One suffer, tired of killing people and monsters, tired of fighting an endless war. It's very possible that working for Providence is what turned Six from that shitty, cocky guy he was 20 years ago into the tired soldier he was when he met Rex. He saw hope, an opportunity to save people, to save his father and bring hope to the only other person who seemed to care about EVOs beyond killing them.
And for that, Rex suffered. White suffered. Six watched the man he loved be forced into an office and the child and hope he wanted to protect fall under Providence's grasp. He pulled Rex into the life because he wasn't careful, denied him any semblance, any opportunity of a normal life. Six became Rex's protector, but he can't protect Rex from the very thing he pulled him into - the mistake he made because he let hope and desperation drive him.
And...it also makes me wonder. Do you think he feels he doesn't deserve Rex? Do you think his heart drops when Rex jumps headfitst into danger? When he sees the kid hurt on the field, or pushing himself past his limits to save people - do you think Six feels guilty he's in that situation? If he'd been just a little smarter, this child wouldn't be suffering. More people overall would be hurt, sure - but the child he cares about, the child who made him into a better man, would be safe. It's a selfish thought from a man who has only known the selfish life of a mercenary for so long, a man we see selfishly cling to hope with One's suffering.
And part of me wonders if that's part of the reason why he trusts Rex, but he tries to play it by the rules first at the beginning of the show. Thay beyond just protecting Rex, he feels responsible for this current danger Rex is in, and that the best he can do is protect Rex as much as he can, to take the brunt of the consequences of Rex's rebellion and stunts on himself.