Gonna request you rephrase "win condition" to be less misleading. First of all, winning is dependent on the battle itself; for example CM Clef doesn't win the game for you in all matchups, and in those cases trying to win with it is probably not the way to go.
Second, calling a Pokemon a condition in itself is flawed. Here condition is like a prerequisite that needs to be met, so it's more the situation a Pokemon / battle is in that leads directly to a win, rather than the Pokemon itself. This is the way condition is used outside of Pokemon as well, so it's potentially more helpful for new players if it's consistent instead of coining a new meaning.
Loosely I would call them set-up sweepers since that's indeed what they are doing. In general on stall the implication is they are too tanky to take down and thus "sweep" a team, rather than the traditional set up once or twice and OHKO everything sort of sweeper.
You can just say "Pokemon X wins the game" or "a way to (actively) win the battle" instead as well.