I wouldn’t go so far as to say he was a good guy, but I still don’t think it’s fair to label him as a bad guy by the end of the book (pre-prologue). By the end of half blood prince he’d started realizing that he was on the wrong side, but how many 15/16 year olds are out there that have the confidence to openly defy their parents, especially ones so renowned as the Malfoys? Nevermind the fact that Voldemort would have him killed for defecting