What happens to a team's poison counters if an effect causes one of the players to lose them?

When a player on a team loses poison counters, it typically affects the entire team's poison counter total because poison counters are a shared resource in team-play formats like Two-Headed Giant. In this setting, all players on the same team share a collective life total and other game states like poison counters. Therefore, if an effect specifies that players lose a certain number of poison counters, the total number of counters for the team is decreased accordingly, which reflects the collaborative game state between the two players on the team.

The option regarding only one player losing the counters doesn't align with the rules governing shared resources in team formats. The idea that the effect could be negated contradicts the way effects operate within the game, as unless specifically countered or prevented, effects resolve as stated. Finally, saying that the counters are only removed from an individual player’s count fails to recognize that poison counters impact the team as a whole rather than being tied to individual players exclusively. Thus, the best understanding is that if one player loses poison counters, it reflects in the team's shared total.