" the only thing I can’t forgive him for is that he prioritized revenge over his own children" but he didn't? he gave up everything he had to get his revenge to save dean, the colt, the opportunity to kill azazel, his life. he gave that up for his children.
Yes, in the end. But he sacrificed everything else prior to that - he only drew the line at killing his sons. He prioritized revenge above giving them a stable, healthy environment to grow up in. He prioritized revenge above giving them a supportive, encouraging parent figure who could respond to their emotional and physical needs as children absolutely require. He prioritized revenge above ensuring he was there to fulfill the crucial needs that his children had. He prioritized revenge above Dean’s needs, especially, denying him his childhood and forcing him to mature much too early, causing him a whole array of psychological issues he still struggles with. For him, catching Mary’s killer was more important than ensuring that his living children’s needs were taken care of.
Did he provide his children with a roof above their heads, food and relative safety? Most of the time, yes. Did he also accidentally make sure that they were prepared for their fates in the big picture? Yes. Does that excuse the damage he also inflicted upon them? Not in my eyes.
It doesn’t seem like much if you don’t know how majorly parentification and abandonment fucks children up, both in the moment psychologically and in the long run. Good example of how badly their unstable childhoods hurt the brothers is their extreme codependency. It’s not a funny joke, actually, no matter how endearing the fandom finds it. Codependency is a mental health issue that ruins lives, and it’s a direct consequence of John’s parenting, especially regarding Dean. Sam has had most of his needs looked after as far as his childhood went, excluding the long absences once John started taking Dean with him to hunt as well as the inevitable instability of their living arrangements and the fact that his primary caretaker was only four years older than him and couldn’t possibly adeptly respond to his needs as such, but Dean had to sacrifice most of his own needs to offer that to Sam. Parentification is a form of child abuse and it has catastrophic consequences for children, and John is one hundred percent guilty on this account.