Frustratingly, thanks in part to the mixed fortunes of the DC Extended Universe, most tend to consider the DC universe a decidedly darker place than Marvel's. While it's true there's an aesthetic and even tonal delineation between both publishers, both practice their fair share of dark storylines. It's never really been the case that one company strove to be 'edgier' than the other, and if there was, the closest example would probably be late-nineties-early-noughties Marvel.
Still, for all there's a general sense of parity when it comes to the mix of tones on display across either side of the Big Two's divide, DC's darker elements are certainly telegraphed more prominently. Their biggest mascot is Batman, and as far as origins go, they don't really get much darker than his - unless your name happens to be Frank Castle.
But while that may be the case, like Marvel, the DC universe is also home to some characters you wouldn't really expect to have emerged from tragic beginnings. Some were hidden beneath the surface, while other stories were there all along, and simply took a moment of reflection for readers to realise that yes, maybe a child raised by a torturous grannie-general would maybe have some issues as they grew older.
Either way, all of the following characters share common ground in that their personalities all belie a darker past, one DC are only just beginning to grapple with in some instances.