Maybe “evil” is a word with too many connotations. Let’s try “bad”. If a character is “bad” in the Potterverse, then they will be the same level of “bad” 100% of the time, whether that level is “being obnoxious and sucking up to authority” or “casual murder of anyone who gets in the way”. They will never display moral complexity unless their name is Severus or Draco.
I’m reminded of the attribution fallacy. The protagonists act well or badly in response to the circumstances they’re in. The antagonists have “badness” of one sort or another as an integral feature of their character, and all their actions reflect it.
Maybe “evil” is a word with too many connotations. Let’s try “bad”. If a character is “bad” in the Potterverse, then they will be the same level of “bad” 100% of the time, whether that level is “being obnoxious and sucking up to authority” or “casual murder of anyone who gets in the way”. They will never display moral complexity unless their name is Severus or Draco.
I’m reminded of the attribution fallacy. The protagonists act well or badly in response to the circumstances they’re in. The antagonists have “badness” of one sort or another as an integral feature of their character, and all their actions reflect it.