I'm wondering what characters have a +2 or -2 perplex ability. So far I've found
DC75 Sinestro
BatB Black Hand
WoS Doc Ock
HoT Gharsyskt
SI Mr Fantastic

is there any more I'm missing?

I know of Dr. Strange and Adam Warlock from SI and Riddler and Chang Tzu from AA

Saint Walker from DC75 has a +2 perplex but it is only for characters that have the Green Lantern Corps keyword.

Detective Chimp from DC75 has a +2 perplex but only when targeting characters with the mystical keyword.

Mr. Fantastic from the starter set 100 points.

Madame Hydra
Convention Wonder Woman

Mouth of sauron

(Damage) Demoralize: Mouth of Sauron can use Perplex and Probability Control. When he uses Perplex he can modify combat values only by -2 and he does not need line of fire to the target if the target is within 5 squares.

he's one of the few that can double perplex down damage

Psycho-Pirate from Crisis can use perplex, but can only perplex by -2, so just like DC75 Sinestro.

Also, it may not be exactly what you're looking for, but Circe has a unique perplex as well: she can perplex herself and another friendly character if it is the same combat ability, but still only by +1. So overall you get 2 perplexes, but not on the same character.