frankly the only ones I think are smart are Ursula & Queen

She did nothing smart

I don't see how the queen is smart, because she just relied on spell books. I think Ursula and Mother Gothel are the smartest.

The queen and Maleficent did nothing special, and would've been lost without magical powers. Other than Rupunzel's hair and her escape from the castle at the start, I don't think we saw Mother Gothel do anything magical, yet she still is up there with the best disney villains.
Sorry for going on ;-p

Mother Gothel is the least smart, and I will always choose her when it comes to this question.