It is not, however, a problem we need to keep expanding. It is okay to have some heroes with this kind of background. It is, after all, an actual reason why people go out and raise hell. But there are other reasons, and other kinds of heroes.
An Army of One has a bunch of characters, assorted genders, and none of them have a specifically fridge motivation. There was one big massacre, but I think everyone was already involved somehow before that happened.
Beneath the Family Tree is largely nonviolent, aside from period-typical threats from animals and weather. Mostly they're inventing tools and civilization.
Clay of Life has one male and one neuter lead. No females were harmed in inspiring these heroes. Yossele simply ran away from an abusive master.
A Conflagration of Dragons is rather the opposite: lots of characters of various sexes, but no heroes. The dragons have pretty much wiped them out. The survivors are the ones who ran like hell.
Feathered Nests has genders all over the place, but the only person who gets seriously hurt is male.
Fiorenza the Wisewoman is a female lead with a life of average-type tragedy. Her female relatives died while she was a teenager and left her as the herbalist of the village. Her father didn't return from sea until considerably later.
Frankenstein's Family -- amusingly, Victor is lying about his "dead wife" to conceal Adam's true origins. Some women have come to harm in the series, most notably Csilla, but she's not particularly heroic.
Hart's Farm empties the whole QUILTBAG. Most of the characters are healthy and happy. Auduna gets off to a rough start but is soon fine. It's a great place to heal. I think the most fucked-up person is Ragi, who is a gay man.
Kande's Quest most definitely has a hera. She is inspired by the kidnapping of her baby brother. Stuffed in a clothes dryer!
Kung Fu Robots has Eastern-type heroes. They are questing for enlightenment. Almost all are neuter, and I don't think any females were harmed in this series.
Monster House has a family of humans and monsters of various genders. Some of the harm is dark fantasy stuff, but little of it drives anyone to heroism. There was that time the bogeyman ate a couple of people for abusing their daughter, but that's about it.
The Moon Door is based on a women's chronic pain group, so all the women have been or are being hurt terribly. It doesn't drive them to heroism. It drives a bunch of them to lycanthropy. Problem mostly solved.
The Origami Mage has two female leads who are rivals. Aside from the paper magic it is a pretty ordinary rivalry with no heinous happenings. They're just arguing over the One True Way.
Path of the Paladins features a world in ruins. Two female leads, one inspired by vocation and the other by rape. Johan and Althey, both male, are also heroes. There are assorted other characters too. Real live heroes! But only one with a fridge-type background.
P.I.E. has a female lead and a male sidekick. Brenda uses a wheelchair after a serious accident. It doesn't slow her down or make her unhappy. She just likes to solve weird crimes.
The Steamsmith features a genderqueer lead. Her mother died as an infant. That's sad, but it's not driving her to heroism. She's the daughter of a nobleman, hence her leadership training; and she loves alchemy.
The Time Towers has various gendered heroes seeking to make the world better through time travel. No fridging involved.
Walking the Beat has two female leads, one of them a retired hero for medical reasons.
Polychrome Heroics has heroes of all kinds and genders. Most are not driven by a bad past. But look at the supervillains. Quite a few of them are, and some of those involve injured or dead women.
So out of that whole pile, only a handful have anything close to the background that everyone else seems to be writing. Hey, that means less competition for me. :D