Lots of superheroes are “children of the atom” in the sense that they derive powers from some sort of radioactivity (think Spiderman or Hulk or even Daredevil) while others are just born with powers without explanation (X-Men, Thor, Superman, Aquaman, Wonder Woman).
Who is a superhero that is somehow grounded in reality, meaning that they could “potentially” make sense (either their origin story is believable, even if it has some obvious gap to make a super power happen, or their power is somehow limited or constructed in a “reasonable” way).
I guess with these restrictions, Batman would be OK since he’s got no superpowers, but he’s insanely rich and therefore can both train himself and have access to sophisticated gadgets, but can you think of less obvious ones (even if they’re minor characters)?
Thanks for reading this!
Edit: thanks for all the answers and apologies for the slow replies. I’ve had a couple of complicated days. I’ll now go through answering you. Several people made me realize I hadn’t been precise in what I meant and helped with their answers. I was looking for superheroes or superpowers that are somehow “believable” in that they’re either constructed in an unexpected way or in a way that you could almost accept as plausible
Hawkeye and Black Widow are examples of what I was looking for, thanks! They are normal people with extremely good training.
Daredevil is one I was kind of ruling out in my original post since he gets his powers from chemicals spilled on him, so it feels a bit like a “deus ex machina” plot device, like being a mutant or an alien or touching something radioactive. EDIT: on second thought, you’re right that it’s known that if you (unfortunately) go blind your other senses somehow help you make up for the loss of sight and so it may be believable that by chance the chemicals he was wetted with could somehow heighten his senses, so actually Daredevil is more in line with what I was looking for than I initially thought!
Poison Ivy and Mr Freeze are amazing answers! Poison Ivy is “believable” in that she’s grown immune to poison because the mix of herbs she’s taken “could” have an unexpected effect and Mr Freeze too is awesome in that he’s a scientist trying to save his terminally ill wife with cryogenics and somehow the experiment goes wrong.
Now you’re also making me think about the very first episode of the Batman animated series where a scientist researching bats is turned into one.
Your answer suggests that a source of “believable” origin stories are experiments gone wrong, if the experiments are somehow well thought and resembling actual science
Edit: updated my thoughts on Daredevil after reading another answer on para humans in this thread.