Well, if I'm supposed to answer only with characters I actually play in games, I'm a little limited at this moment.

THAT SAID, Rachis still wins a top slot! Though they probably don't have it worst, that's probably a two-way tie between Mag and Vosges.

Mag Ransom is a Changeling: the Lost OC, and just by virtue of being a C:tL OC has one of the worst pasts ever. /)_(\

>He and his two brothers sign up for the draft in late 1940

>Before he can get drafted, he gets abducted by Fae

>Gets delivered to crazy doctor, has all his blood removed, then gets extensively and impossibly surgically experimented on

WORSTTTT

>Gets taken to the Terror Mines for god knows how long, made to dig without rest, food, or drink, being warped simply by BEING THERE, before finally being left for dead in a cave-in

>Eventually digs his way out of the cave-in and out of Faerie only to find it's 2012, his hometown doesn't even exist anymore, and most if not all of his family is dead

rukafais: IT REALLY IS THE WORST, there are no happy stories in Changeling 8(

Then, of course, there's Vosges, from The Knife of the Traitor.

Whose entire village lived in a demanding dictatorship and his people were driven like slaves to produce for the kingdom

until when he was still just a kid the new ruler had his entire village burned to the ground and everyone in it killed

except for him, who she imprisoned in a castle basement.

She attached a parasite to him that made it impossible for him to ever age, and made it so he couldn't eat anything other than feces, and dropped in a load of books (most of them magic books!)

WELP

but made sure that a good chunk of them were fakes without telling him.

And then left him down there for years.

Painwheel probably gets third place actually. But Rachis is a solid fourth! And The Batman's Riddler rounds out the top five. uwu