Games with “little brother” modes, i.e. simultaneous two-player mode where the second player is inconsequential for the most part… looking for lesser known ones such as…
Kirby can spend his copy ability to create a player 2 character with that ability. When the player 2 character dies, Kirby can just create another one. Whenever Kirby gets a health pickup, within a short window of time he can go touch player 2 and share the health gain with him, by literally kissing him and vomiting the food into his mouth like he’s a baby bird. Great system.
Player 2 controls Bandana Waddle Dee, who has no abilities beyond spear stabs. He can die but he comes back after a short while at no cost. Kirby 3 had a similar ally but re-summoning him had a cost IIRC
A second player can take control of the sumo, and can either use them to hinder the player, or help them by taking care of the ninja. Either way, there’s little consequence if they die as they just respawn.
This one is more of an edge case, I think… one player is the professor, and the second controller moves the gates up and down. So, they can’t die, but can kill the first player or screw them if they don’t move the gates at the right time.