Have you tried asking the original owner if they want them back? I think that’s always a good idea if they won’t take offense to it. But you own the OC now, so you can really do whatever you want with it, even delete it. I don’t think most people think it’s that big of a deal.
I've got a handful that I've tried putting up for free and everything and I still can't get rid of them, atp I just want to send them into the abyss and delete them but I'm a little unsure as to whether that's okay or taboo on this site cause they aren't my designs
it depends on the designer i feel like, some people dont care and others do. i personally wouldnt, but they are your characters, so if you wanna delete em you can! also have you advertised em in those looking for free character posts some people make?
also how picky are you with who you give them to since theyre free? like do you care about who gets em at all? bcuz i could take them if you just wanna get rid of em :P