Fantastic Science: Koura may be a user of this. While he clearly uses Black Magic (like animating the figurehead on Sinbad's ship), he also seems to use a form of chemical explosive to trap Sinbad in the cave on Lemuria.
It was actually Baker's stunning performance as Koura that brought him to the attention of the Doctor Who producers when they set out to find a new Doctor to replace Jon Pertwee.
Too Dumb to Live: YMMV on this, but Sinbad and his crew trying to sword-fight Kali, a statue made of stone (or metal, it's hard to tell). There is no way that swords could hurt it, and they have to knock it off a ledge to break it, anyway. Why not try to run or draw it out of the enclosed temple?
Uncanny Valley: The centaur's all-too-human screams unnerved some viewers.