Does this mean Giant Man's use of his special power limits the overall modification of a combat value to +2, or when GM uses Perplex he gets to modify a single value but it is modified by +2 instead of +1?

Ares has similar wording...

/thanks

both modify whatever number by two with each use. its like two uses of perplex together.

and GM can only use it on a single target.

ex: GM uses Genius on Ares Damage, and Ares uses Tactics on his own attack = Ares at +2 dmg and +2 attack.

The wording implies that the use of Perplex is all or nothing. That is, when you modify values it must be by +/-2. You also couldn't split the bonus between two different stats.

When would this be anything but a good thing? How about when you're attempting to use a heavy object(+2) and the 'super' perplex(+2). Because objects add to damage value now you are limited by the Rule of 3 and cannot get the full benefit from your powers.

But it's still not really a bad thing. You can still use both of the +2's, it just caps out at an effective +3. (Some other posters have been mistaken on this, thinking that you couldn't attempt to apply the +2 if you had already utilized Perplex twice, for example.)

Actually Giant-Man cannot modify a stat by -2 - it's +2 or nothing.

agreed, it says so right on the card