Helldivers is a truly fun coop game with a sense of community. The learning curve is steep, however, but if you stick with the game, you will feel rewarded.

I distinctly remember struggling initially with low-level planets, just to later be able to clear lv. 12 planets while casually chatting with my team-mates without any issues.

Definitely a game worth trying out if you enjoy cooperateive gameplay and an over-the-top presentation and humor.