It’s not co op but head to head. But if you haven’t played duck game, I feel like you are missing out on some of the best local multiplayer pc has to offer.
If that’s too competitive, try Ultimate Chicken Horse - if you want some incentive watch a guy named Northernlion play it on YouTube
Next on the semi co op is Crawl although it’s still a little competitive, I can’t do it justice by describing it but it’s great, videos will do better to describe it.
https://www.penny-arcade.com/comic/2008/05/02/making-an-impression