Savages - Pocahontas: I don't watch Pocahontas a whole lot but out of any songs of disney classic movies is this one and Friends On the Other Side.
Oogie Boogie's Song - The Nightmare Before Christmas: Oogie Boogie is one of the best Disney Villains! How is this song not higher up on the list.
Mother Knows Best tangled: Comparing this reprise with the original just makes this even more scary and intense. It shows how Gothel has gone from plain protective to absolutely controlling.
It's Our House Now - Mickey's House of Villains: One of the best unrated song ever made. It's a mixup of all villians songs on once.