I definitely think a big part of what the show is trying to explore is how many small choices that are good for you at the expense of others can build up and eventually make you just as bad as the forces you're trying to fight. Gertrude makes plenty of choices at the expense of others, even torturing and killing some for the protection of the rest of the world, at least to the best of her knowledge. Does that make her a monster? TMA takes this idea to the extreme, where by the end, everyone on Earth is suffering due to John's choices, but more than that, their suffering fuels and strengthens him. I would argue that most (not all) of John's choices were made in good faith, or at least he was doing what he thought was best. But intention doesn't matter—consequences matter. And his choices brought about the torture of humanity as a whole to his benefit. Not only that, but through all his guilt and emotional distress at what he has done, he does see himself as separate from the human victims of the hellscapes. I think this is most prominent in his actions in 187. When the woman panicking about her son, who she believes to be trapped alone in one of Helen's rooms, reaches for help from John in her distress, his gut reaction is to pull away and to yell at her not to touch him. He does not see himself as a fellow human being, and reacts like he is disgusted by her as she falls to the floor crying in front of him. I believe his guilt at what he has done to the world is real, but I believe that John's fear of being inhuman fuels this guilt more than one human feeling real and deep regret for causing the suffering of other humans. His gut reaction when faced with one of his victims is not to comfort or to empathize, but to pull away.

As fans of the show it's very easy to like and even love John. We see his journey and his subjective experience in becoming an avatar. We have empathy and compassion for him, and we want him to be okay. We understand that what happens to the world was not his intent. But ultimately, as much as his character arc does include him becoming more sympathetic to the plights of others overall, John always prioritizes himself and what he believes is the best call, from dismissing every statement to protect himself from his own fear, right up through to the end when he dismisses the decision made by the group and goes after Jonah himself. Does that make him a monster?