Astral Chain, the upcoming Nintendo Switch game from PlatinumGames, has optional local co-op, but it allegedly makes the game more difficult.
Astral Chain’s director Takahisa Taura revealed this information in an interview with Kotaku, saying (via a translator) “You may have noticed that the characters are connected by a chain… when you’re controlling two characters, that chain allows you to see where the other character is in relation to the one that you’re controlling.”
Source: IGN.com Astral Chain's Co-op Mode Makes the Switch Exclusive More Difficult