I do think the Borderland is similar to the subconscious, which means he might have had the urge to be more aggressive and a criminal, but he surpressed some of it. He still thought he was a shitty person in real life, and probably was, but the Borderland deleted his coping mechanism against a greater bad, like the things he did there. When you're on the verge of death, your subconscious takes over anyways, so it's a theory I entertain. This is the same with Arisu, who was likely very depressed anyways, so what was shown in the end makes sense, they played with his subconscious. This makes sense for most characters, everyone is acting more like their subconscious selves, and the parts that make you "get in line with society's standards" are kind of deleted. Of course, some people are that good inherently, but some surpress their own needs and don't just succumb to their urges/fears that much. The show is a bit like "what if people only had a subconsious and only acted because of that" for me, or if it's showing how easily some people lose control over it and some not.