In an origin that could only come from a comic book, Dr. Alex Sartorius is touring a nuclear power plant he helped finance when the core explodes. Sartorius takes cover behind some sand but the explosion blasts five million "slivers" of sand into his body, but... well this can only be explained with a direct quote: "but not -- hee hee -- ordinary sand! No! Radioactive sand -- blasted upward one level on the atomic scale! Atomic number fifteen -- silicon -- became number fifteen -- phosphorus!" I'm no physicist, but I'm pretty sure that's not how radiation and atomic numbers work.
Doctor Phosphorus was suggested by First in the comments, and when I said I wasn't that familiar with the character, First mentioned that he loves to let people know that he "burns when exposed to air." And that he does. He only mentioned it three times in his two issue origin story (which also introduced Silver St. Cloud, one of Batman's long term love interests), but it still felt repetitive. But as you may have guessed, Doctor Phosphorus's power is to burn when exposed to air.
Anyway, he blamed Gotham City for voting not to fund the nuclear plant, forcing the construction to cut corners which lead to the explosion. So he took out his revenge by swimming in a reservoir, poisoning Gotham's water supply with phosphorus. In the end of his first story, Doctor Phosphorus takes a long fall and Batman, despite a 40 year history of villains returning from the dead and/or escaping from prison, happily assumes that the Doctor Phosphorus problem is solved without bothering to look for a body, and goes off to hit on Silver St. Cloud.
Pros: He burns when exposed to air!
Cons: He burns when exposed to air!
How I'd do it: The closest I can think of is a guy with radiation sickness blaming Batman or Bruce Wayne for whatever accident is going to kill him. But, sadly, he wouldn't burn when exposed to air because that's far too fantastical for these movies.
Casting Guesses: Dr. Sartorius has one of those weird thin mustaches that no real people have except for John Waters, so the only actor I can think of is Matt Dillon with his There's Something About Mary 'stache.
Verdict: Sorry, but no. Doctor Phosphorus could've fit for last week's parade of never-gonna-happens, but I didn't get a chance to read up on him until now.
After The Scarecrow, Ra's Al Ghul, The Joker, and Two-Face, who should be Batman's next enemy in the Batman Begins/The Dark Knight series? Well, as of now we know that Tom Hardy will play Bane and Anne Hathaway will play Catwoman.
Check out the master list for all the villains covered. I've pretty much run out by now. Obviously, there are more Batman villains, but not any of significance that I know of. As of February 2009, no one is confirmed as a villain. Not the Johnny Depp Riddler, not Phillip Seymour Hoffman Penguin, nobody.