A lame duck, in the context of a game, is a player who remains in the game but has no chance of winning. It must be literally impossible— not merely highly improbable — for a player to win for it to constitute a lame-duck scenario. If a game frequently admits lame-duck scenarios, this is considered a severe design flaw.
A kingmaker is a lame duck who retains the ability to select who, among other players, will win the game.