Can't see any option to unfriend someone once I've accepted them as a friend. How's it done?

In your friend list, you just click the down arrow, and select "remove friend" form the popup menu.

Go to your list of friends https://www.gog.com/account/friends (you can find it in the navigation bar, in the menu under your nickname) hover mouse cursor over a nickname, and from a drop down menu select "remove friend".

Nope only see options to view their profile, their wishlist or send a message to them. No unfriend option.

But...but...we were just getting to know each other!

10s and 20s usually help. :)

Just tell them you liked Beastmaster 2.

Sounds like you skipped the part where you go to your friend list.

Don't make this weirder than it already is.

Nope, go into my profile, choose Friends, list appears, hover over friend's icon and only get view their profile, view their wishlist or send a message to them. No other choices.

You're going there https://www.gog.com/u/MedeaFleecestealer but we've been telling you to go there https://www.gog.com/account/friends

everyone is my friend, why bother to make a list?

Lists make things look official.

Go to https://www.gog.com/account/friends, hover and unfriend.

Look at the picture.

If that doesn't work you might want to contact support.