I guess he's just a dominant/wild male, as soon as we brought him home he immediately started harrasing our female adult cat, chasing it and holding it while biting it's neck scruff (he didn't stop doing this until months later). He required no adjusting to our home, and within a week would try...
Pretty sure he's some sort of shorthair mix, but does it look like he was neutered late? The shelter had no information on the cat except that it was brought in by someone and was maybe 6 months old already neutered. His head and nose are quite large compared to our other cats