Worms Ultimate Mayhem

To boost this quickly with a partner you just have to both search Ranked Deathmatch games (or any other ranked mode) and trade wins. The other person can just quit the game after loading in. If necessary, the person still in the round can skip their turn with Skip Go (jumping rope) and after that the win screen pops up.

To be safe win in 3 different modes at least once, but you only need 40 wins in total.