Re: Underpowered tropes?
Is this including Multiform? Because I've always found Multiform to be a gateway to more power than you could possibly need. Shapechange+VPP is also a pretty solid combination.
Speedsters, I agree, are balanced on a thin edge - they often end up either too fragile, or as deadly as the rest combined. And it doesn't help that SPD tends to be an "arms race" kind of stat - once someone bumps theirs, everyone has to follow or be left waiting for their turn a lot.
Mentalists - I wouldn't say they're weak in general, but certain powers are, at least in combat. Because of the whole +20 thing, Mind Control seems more suited to "jedi mind tricking" guards than taking over actual foes. Mental Illusions is potential gold though, Mental Awareness beats a lot of tricks, and Ego Attack is useful against high-defense types. Something like telekinesis/pyrokinesis/probability manipulation is essential though, unless you want to spend some fights on the sidelines.
Robots, incidentally, and inorganic characters in general, can be somewhat screwed by the necessity of taking expensive Life Support. Sure, you don't have to take it, but it's going to look pretty lame when your android falls over from knockout gas. Especially problematic if your archetype is something that's already points-hungry like Speedster.
Of course, Multiform, Duplication, and Summoning can free up enough points to make practically anything valid or even mind-boggling strong (see Iron Will above), as long as your trope doesn't preclude those.