Ok, I am an Axel fan but you miss a few details there. Roxas treated him like crap cuz he hid the truth from him. Plus he wasnt that innocent, he manipulated rikureplica, he killed vexen and zexion, he plotted aalong with saix(Im not saying that all of this isnt cool)
He was just following orders. And then when he DID tell Roxas the truth, Roxas didn't believe him.
Also, in re:com, he didn't have feelings, therefore didn't have a conscience and couldn't feel guilt or remorse. But then he gains feelings, and when he does, he basically gets shitted on by those emotions.