I would like to think that he is morally grey, but mostly a good person. Like, I heavily hc him to have been a down on his luck artist/businessman who had a dream of creating Dandy's World as like a puppet show/animated Tv show (like Sesame Street or something). However, he could never find a way to fund it, as he was continuously rejected by potential investors. When he met Delilah, she, with the help of the ichor, was able to expand his dream in a way he never thought possible. Really, I feel, he's not an evil person, just a guy who wants to achieve and maintain his dream.
However, I do feel in that wholesome desire lurks something more ugly. I kinda got the feeling in Delilah's note to Arthur, where she states that Bassie could not be a main, as her word choice implies that her concerns were brought up BEFORE she was released to the public. Yet, they continued anyway. While Delilah's note seems to have heavily influenced Bassie, the fact that Arthur must have refused, enough to override his founder's concern, makes me think that Arthur is heavily invested in seeing his dream pan out, even if it means potentially harming the health of the toons he creates. (I/e "They can't be sad/upset/angry at their position in life! I made them happy; they can't have more complex feelings than I allotted!")
I also feel as if he is the kind of person to get drunk off of his success, getting more and more boundary pushing the more he succeeds, as he feels more confident that he can get away with pushing a boundary. However, there really isn't any evidence for that, just a feeling I had.
Part of me feels as if Arthur is one of the factors that caused the Twisteds to show up, like his management and desire to expand his dream either caused Delilah to create them via a mistake or argument, or his own hubris created them.
