Not posting the actual music because I'm too lazy but I'll give titles as examples
FF6: The Decisive Battle, Kefka, The Wedding Waltz. Everything about it just works and Kefka is just damn creepy.
FF4: Golbez, All the Villain themes are awesome, and Golbez's big pipe organ theme is just Bad Ass.
Anything Shoji Meguro puts out from the bitching guitar riffs in DDS, the Jazzy Devil Summoner, and the more J-pop Persona 3/4. Examples: Who's there?(P4) Hauntingly creepy and awesome. Raido's Theme, though it did wear out it's welcome in the final battle of Devil Summoner 2, Divine Entity(DDS2), and Burn my Dread(P3).
Castlevania: Portrait of Ruin:Some people didn't dig the drum and fife style but I absolutely loved every tune in the game, all catchy as hell. Examples: Crucifix Held Close and the remix of Simon's Theme.
Tales of Legendia: Excellent Soundtrack that too many people missed out on because of the sub-par art design and gameplay. Not listing any example, go to youtube or play the damn thing, it's worth it.