if you like FPS:

Left 4 dead 2

dead island definitive collection (cheaper on fanatical.com)

dying light

borderlands 2 (cheaper on fanatical.com)

borderlands the presequel

Might need to make it clearer if you mean local or online co-op :)

For the King - up to 3 player co-op
Chaos Reborn - up to 6 players it is technically not a co-op game but you can assign teams to your liking. I highly recommend playing the "Classic Chaos" mode - it is the most fun but there are plenty of options to choose from.

Ben and Ed Blood Party, works great under Proton

Quoting: Liam DaweMight need to make it clearer if you mean local or online co-op :)

Due to pandemic and my city being in quarantine, im looking for online co-op

Quoting: DefaultX-odBen and Ed Blood Party, works great under Proton

I didnt understand anything about this game but it looked really fun

Quoting: SchattenspiegelFor the King - up to 3 player co-op
Chaos Reborn - up to 6 players it is technically not a co-op game but you can assign teams to your liking. I highly recommend playing the "Classic Chaos" mode - it is the most fun but there are plenty of options to choose from.

The "For the King" seems interesting. Thanks for the recommendation

Quoting: sergeif you like FPS:

Left 4 dead 2

dead island definitive collection (cheaper on fanatical.com)

dying light

borderlands 2 (cheaper on fanatical.com)

borderlands the presequel

Left 4 Dead 2 its one of my favorites games of all time, but my friends are not fans of zombie games.

But Bordelands they will definitly like

I am currently playing a lot of Northgard with my friends, a reasonably chill RTS. It isn't co-op per se, but we only play it cooperatively - i.e., as a team of 3-4 against a team of AIs (due to: we are a bunch of carebears that don't want to compete with each other and backstab and etc) and it's really fun. The game has a very punishing environment (harsh winters, neutral factions, kraken attacks, etc) so it doesn't get boring by not having human opponents.

Quoting: WJMazepas

Quoting: DefaultX-odBen and Ed Blood Party, works great under Proton

I didnt understand anything about this game but it looked really fun

And it is!