All of them.

Kept seeing the "Steam Games You Can Play Without the Steam Client" thread here, now with 15 pages of responses, so thought I'd keep things in perspective.

As far as I can recall, one cannot play Gwent without the client (haven't tried it though). So, all of them -1.

Also that one multi-player only game that requires Galaxy to play. I forget its name.

Well that isn't true, so you now just look like a smarmy prat trying to be a smart arse.

Also, The Witcher 3 disc wouldn't install without first installing Galaxy on day of release. I assume that hasn't changed much being a disc and all.

Someone is temping fate...

Gwent?

Gwent is still in Beta, so it doesn't count....yet.

Hope is the last thing to die.

Isn't Galaxy essential for Absolver. I thought I read that somewhere in the forums.

And Xenonauts 2 Demo. So, all of them -2.

And?

Gwent
Almost totally absolver.
To a large degree: witcher adventure game, goblins inc
For some, latest version/updated e.g. Riven (not sure if that's changed now)
For a large percentage any multiplayer
There is likely other ones and I am sure cyberpunk will be totally online only

Nex Machina is broken without Galaxy, since you can't save your high score. The Arena mode and visual upgrades are also dependent on Galaxy.

Also, I have to dodge the Galaxy installer each time I download a game. Which isn't all that hard, of course, but it's a passive-aggressive reminder that GOG really doesn't appreciate that you play your own DRM free games without being constantly connected.

Absolver has a single-player mode that can be played offline without Galaxy. It's not very good, but it is there.