It seems like this has been asked before but with no clear answer. Is there a way to perinatally delete a purchased game in my library? I understand that you can hide a title, but is there a way to completely delete it?

No, not yet.

You could ask the customer support.

You can, but you really should not.

GOG does have a hide feature, but it's half-implemented.

Go to your account, find the game, and select the hide option.

https://www.gog.com/en/account

Probably the best option is to do that, but have them convert it to a gift code and send that off to BenKii for the community GA. That way, two or even three people can be made happy: you, for getting rid of the gunk while having done something nice on top, BenKii for being appreciated and able to offer more variety, and the yet-to-be-determined giftee for receiving a free game. :)

One of the only times you'll hear perinatally in a sentence when describing GOG.