The God Damn Man-Bat
The Batman's villains are all pretty ridiculous but you can make some sense of them. The Penguin is a sad deformed child who uses class to become one of Gotham's most feared kingpins of crime, Two-Face is an honest man done wrong by the justice he worked so hard for and now sees both sides of the law and even The Joker is only as insane as the clothes he wears. The brutality and overwhelming numbers of his murders are as unbelievable as his get up. Man-Bat however, is just a monster.
Batman: The Animated Series as far as I'm concerned is the best representation of almost all Batman villains and the man himself. Man-Bat especially came into his own in the first episode of the series, "On Leather Wings". Dr. Kirk Langstrom is a biologist who hopes to prolong human life with experiments using bat genes. Langstrom uses himself as a guinea pig and turns into a half-man half-bat beast but realizes without the ability to control himself in this form it's useless to him, and dangerous. He tries to end the trials, but the part of him that became the bat feels differently, forcing the Man-Bat out to steal the chemicals needed to cause the change again.
Where Werewolve's transformations are caused by a full moon, the beast inside of Langstrom forces him to become Man-Bat nightly. Instead of running blindly in a blood rage, Man-Bat is on a mission, making him far deadlier to anyone he comes in contact with. Langstrom basically goes into these 'roid rages when in need of a fix, and the only person he really cares about even after the change is his wife. After Batman figures this all out, Langstrom downs a vial to make the change, but when his wife walks in, his embarassment sends him to the skies, Batman in tow.
Batman's usual "brains over brawn" techniques don't work in the skies, and with Man-Bat's strength the Dark Knight can't get an edge. Man-Bat's rage and confusion leads him to fly around the city aimlessly, just trying to get rid of Batman and make a get away, and in his panic he gives Bats the chance to get a few punches in. Crashing into a wall and the aerial fight ending, Batman bleeds for the first and last time in the series. Instead of turning Langstrom over to the surrounding police, Batman cures the scientist of the beast in his blood, and hopes he stays clean off the bat-junk.
The ending of the story makes Man-Bat feel more human, but you don't feel bad for him. He's the annoying kid at the party that Batman has to take care of just so a couple months down the line he'll see him passed out next to the toilet with a dick drawn on his face, his wings covered in vomit. Being given no response from Langstrom after being cured makes you wonder if he liked being Man-Bat more than human and that was why he kept going back to it. He was able to fly and could kick Batman's ass, it's like PCP but it wasn't in his head, he was actually doing it.
All I know is that it produced the second most played with toy of my childhood.