Who is the most plausible superhero, and why? I’d guess the answer to this question would be one of the non-superpower superheroes, like Batman or Iron Man, so as a bonus question who is the most plausible of the superpower superheroes?
Early days Punisher. Nothing but a tough guy with big guns and a kevlar suit who didn’t fight supers other than Daredevil.
As far as superpower heros go, I’d say Green Lantern: billion-year old aliens with Clarke level technology give a human a thought-controlled force field projector that can do almost anything a human can mentally envision.
Not Batman. Not Batman AT ALL. Iron Man’s little better.
Blue Beetle (Dan Garret(t) and Ted Kord) versions are better. Captain America could work with some minor tweaks to his origin.
For superpowered…the various versions of the Flash are fairly reasonable, once the Speed Force is introduced, and making allowances for the existence of a semi-sentient extra-dimensional force/space/entity…their power levels are pretty extreme by the time the Wally era ended, but the people gifted with the power follow a reasonable learning curve for it, have reasonable skill-sets both related and unrelated to their powers, develop plausible secondary powers, and especially in the case of Bart Allen, have logical side effects, both positive and negative.
Except doing squat about anything yellow. 
Does Kick-Ass count? He’s a crazy kid who dresses up in a wetsuit he bought on eBay, but is easily taken down by the gangs of thugs that superheroes normally face, and ends up beat up all the time. His best ‘power’ is a steel plate that supposedly protects from concussion.
By ‘most plausible’ of the superpowered ones, do you mean which one is physically the most plausible. I’d think the Flash is a good one for that.
Kick-Ass is more plausible than Hit Girl.
Dollar Bill from Watchmen.
I guess Iron Man’s suit is technically plausible.
On a text page introducing the Punisher character’s series, the editor noted that if you or I were to one day fight crime, this (The Punisher’s) is the way we would certainly do it. There is no credible reason for Batman to eschew guns or leave someone like the Joker alive.
On the other hand, I always thought the Rocketeer had the most plausible motive for fighting criminals and spies: to impress a really good-looking girl.
Plausible in all respects I suppose. Mostly scientifically, but also other things. For example, even if you put aside all Batman’s abilities, technology and… luck, you still have the police sanctioning a vigilante in a costume.
At the risk of looking like a massive noob I realized I actually know only a small fraction of all the superheroes out there, so most answers here will not make much sense to me. But if we’re talking about superpowers or technology, some detail about what they involve and how it could potentially work in real life might be interesting for me and anyone else who isn’t familiar with the character in question.
Ralph Hinkley.
Has no powers of his own, the suit provides them. Loses instruction book, has to find out what he can do by trial and error and the powers themselves require practice to master.
Not totally sure he counts as a superhero, but the Scarlet Pimpernel seems rather plausible to me. As does (the unpowered, print version of) the Shadow, Kent Allard, who success in crime-fighting is due primarily to his being awesome.
I only saw the movie but didn’t he also have nerve damage from being hit by a car which gave him some minor resistance to pain? That’s… sort of… a “power”. I wouldn’t try it at home, though.
Zenith: what if the world’s only extant super was a dim, spoilt, self-obsessed pop-star/celebrity? Classic series, sadly locked in legal oblivion, still crying out for a movie: Justin Timberlake vs Cthulu…
I can’t recall her name but there was a girl that dressed up in a superhero costume but all she ever did was call the police if she spotted crime.
I always thought JFK Jr. was our one chance at a Batman-esque hero. His life went a very different way though.
And it’s done in one. The first response nailed it.
The Phantom (the Lee Falk comic strip, the guy with the purple outfit in Africa) might fit this, as would good ol’ Zorro. (swish-swish-swish.) The Shadow, even with the power to cloud men’s minds, might be vaguely plausible (illusionist, hypnotist.)
I don’t think so. A lone man on the run wouldn’t have the ability to find out which of his targets deserve their fate and which were undercover cops, and anyone using his methods couldn’t help but kill untold numbers of innocent bystanders.