Morality explained. While you can make certain choices and use spells that may be considered morally questionable, you cannot canonically be evil in Hogwarts Legacy. Essentially, there's no version of the story where you'll be recognised as inherently evil and rise up as a proto-Voldemort.
Otherwise, those set in their ways can get Hogwarts Legacy's evil ending by instead replying with "This power should not be kept from the world" or "I want the power for myself." When choosing the latter two options, there are some notable changes.