Sinister Villians
The best Sinister Villians are usually the ones who use subtle, discreet tactics over a long period of time until the 'final phase of the plan' is ready.
Example;
(I was GM ing) an NPC named "White Witch" (Samantha Stevens Bewitched type) who had a hunted (Black Enchantress) These two got caught up in a fight on the streets of the western most part of the city.
It seems she needed to kill 1 person in each section of
town to achieve 'great power'. Well a PC happened along and tipped the balance, Black Enchantress was destroyed. But as a final DIABOLICAL act she used MIND CONTROL to have her spirit rest in White Witches subconscious, until she could recover.
I dropped subtle clues ,that something was wrong, over the course of several adventures. Finally the PC's & NPC's were captured by a Satanic Cult and were being prepared to be sacrificed on an altar to a Demon named "DIS-the Destroyer"
All the cumulative stress was too much for White Witch and she fainted, out came Black Enchantress and a large melee occured. (Nasty enough for you or would you like to hear more???)