However, I think there's more tragic origins out there. And I'm going to prove it right now because proving stuff like this is obviously cool and almost guaranteed to get me laid lots, right? Well, probably not but I'm going to prove it anyway.
Matt Murdock/Daredevil.
Matt Murdock had a pretty shit time of it. He was raised by his father, a washed-up boxer, for the early part of his life. Then an industrial accident caused him to go blind. Not easy for a kid to cope with at the best of times but, as Murdock was soon to find out, this was nothing like the best of times.
His father, 'Battlin'' Jack Murdock, was murdered by some hoods at the request of their boss 'The Fixer' for refusing to throw a fight leaving young Matt blind, alone and pissed off.
What's more, nobody told him that his first costume (the black and yellow one) sucked.

Daredevil started life as a hero after bereavement and a disability. That's pretty tragic, no?
Jonothon Starsmore/Chamber
Jono's origin was pretty grisly to say the least. Hanging out at a nightclub with his girlfriend when his mutant gene decided to kick in the resulting explosion of psionic energy (no, me neither) crippled his missus and ripped a hole in him from his naval to his jaw. He doesn't have the sort of power you can really hide from people as he's missing half his face and it's no wonder it made him depressed. He can't even have a snog, poor sod.

Arseface.
The cult comic series Preacher was chock-full of tragic characters, perhaps none more so than Arseface. Son of the local sheriff and a big Nirvana fan in a redneck town, he was horrifically bullied along with his best friend Pube.
After hearing about the suicide of his hero, Kurt Cobain, the pair decide to follow suit and shoot themselves in the head to end their miserable existences. Whilst Pube is successful and kills himself as intended, Arseface is not and leaves himself horribly disfigured for the rest of his life. And yes, his face looks like a rectum - and that's never easy.

Wade Wilson/Deadpool.
The Merc with a mouth is renowned for being one of comics funniest characters but his back story is not so full of laughs. After losing his mother to cancer and getting the snot beaten out of him by his abusive father, Wade Wilson turned to the slightly unusual career of being a mercenary. Then he contracted cancer himself and became part of Department K - an off-shoot of Weapon X.
Deadpool is a scarred, mostly insane character that has had far more than his fair share of tragedy... 2 lots of cancer and an abusive parent has surely got to qualify as a bleaker start than Batman's.

There's a start anyway. I'll think of more later.