My favorite is Bog king from Strange Magic - Has a song talking about how evil he is. But all he does is prevent the spread of dangerous mind control magic, and quarantine people under the effects of said magic. Yes he greatly annoys people doing so, but honestly? If I get hit by a love potion, please quarantine me.
Melkior/Morgoth, they saw that Arda was a deeply flawed creation and attempted to correct it before existence was sung into being.
After the fact their actions are certainly viewed as evil by the world they tried to change but had the rest of the Vala joined his song the world simply would have been different, not worse.