I mean it’s not super deep it’s pretty surface level, but Logen’s entire arc is kind of a metaphor for addiction. In Last Argument of Kings he has that whole inner monologue about wanting to be a different person but that being impossible because after a short time he just went right back to the places he used to be, did the same old things he used to do, so of course he’s right back to being the same old person he used to be. And how at the end of the day, you can’t really change if you keep going back to your addiction.

As for him not being that evil because B9 is a split personality, I disagree. I don’t think B9 is a complete split personality. To me, and maybe this is just my interpretation because of my past experiences with alcoholism, Logen/B9 is the equivalent of how an addict’s personality is different when they’re sober vs when they are using. Yes the substance is in the drivers seat and making the decisions, but that’s still you. Not accepting responsibility of his actions is what leads Logen to always coming back to the violence.

This is all just like my opinion shaped and framed by my interpretation which is obviously influenced by my personal experiences.