Ned Creegan, better known as Bag O'Bones (and later Cyclotronic Man and Meltdown), first appeared in 1967's Batman #195. He was just a common criminal until he came up with the brilliant idea of stealing radioactive jewels from a Dr. Logan, mad scientist. While trying to pawn said jewels, Batman and Robin burst in and some combination of shock and radiation transformed Creegan into Bag O'Bones, a glowing purple skeleton with translucent skin, increased strength, and an electric grip. He easily defeated the Dynamic Duo, but disturbed by his new appearance, Bag O'Bones rushed back to Dr. Logan's lab where the not-so-good doctor explained that he'd been working on a cure to radiation sickness to sell to the Soviets, and that for every second Creegan remained in his skeletal form, it was costing him a day of his life. Dr. Logan then offered him a pill that would temporarily revert him to his human form in exchange for being his guinea pig. Desperate to live, Creegan agreed. He also decided that since prolonged use of his Bag O'Bones powers would kill him, he would use them for one big score that would make him set for life. Batman and Robin intervened, and having figured out how his powers worked quickly defeated him. Unfortuantely during the fight his pills were destroyed, and terrified by his rapidly decreasing lifespan he tells them where to find Dr. Logan. When they arrive at the lab, Dr. Logan attacks the Caped Crusaders with mutated animals, who they also defeated, and everybody went to jail. Later, Creegan's powers mutated and much stronger he fought Superman and Black Lightening as the Cyclotronic Man, before they mutated again and he fought Batman and the Outsiders as Meltdown, after which he got the cure he so desperately wanted and was never seen or heard from again.
Let's start with the bad, since frankly there's more of it. While it's pretty clear from the panel to the left that the writer didn't intend this, but assuming Ned Creegan is 30 years old and would have lived to the ripe old age of 90, that still means he can only survive as Bag O'Bones for about 6 hours. Easily an hour of that is spent in his first appearance. That's a pretty big limitation in a serial medium where popular villains make multiple appearances a year for decades at a time. Which is a pretty nice segue into Bag O'Bones second big problem as a character: in three total appearances, he's appeared with three different names and three different power sets. Besides the fact that the comics make a point to remind you that it's the same guy, there would be absolutely no way to tell. Tweaks to a character between appearances are fine and inevitable over the course of years and multiple writers and artists. But while the Joker has managed to be a crime boss, prankster, serial killer and back again, you always knew it was the Joker. That's just not the case with Bag O'Bones/Cyclotronic Man/Meltdown.
Which brings us to what works about the character. And what works, despite being ignored in every subsequent appearance is pretty great. Bag O'Bones is Frankenstein's Monster. Sure he's scary looking and potentially dangerous, but ultimately he's just a petty crook who's terrified for his life. The real monster of the piece is Dr. Frankenstein, or in this case Dr. Logan. He created the creature, blackmails him, and then enables him to commit crimes. And again, Dr. Logan was trying to create a cure for radiation poisoning so that he could sell it to the Soviet Union so that they could survive a nuclear exchange with the US, so he was a bad dude before Ned Creegan ever showed up. So forget the flying radioactive schtick, it's pretty lame. But a walking, glowing skeleton is something out of a horror story. A walking, glowing skeleton who's actually being forced to commit crimes by an evil mad scientist is something out of a good horror story. And if you say he loses an hour of his life for every second that he's Bag O'Bones, that gives a short enough amount of time for Creegan to still fear for his life while being long enough for him to realistically reappear in comics indefinitely. A ghoulish slave forced to do his master's bidding.