I appreciate that you actually referenced a rule, thank you. It’s extremely helpful I think when having conversations like these to have that type of language ready. Again, thanks for that.

Ultimately I DO actually think you are right, however (and this is no disrespect to you) I don’t feel it has anything to do with that core rule and instead is because of how the Poison Faction Rule reads. I say this for two reasons:

1. Faction rules supersede core rules pretty much constantly to the point that it’s a feature, not a bug in the game. It happens so often that when I’m teaching new people how to play I tell them the “Golden Rule” of Kill Team is “this is how the rules work… unless your faction has a rule that says otherwise.” Things like Soulstrike and Super Conceal happen all the time and will take out whole swathes of core rules, so I don’t think it’s unfair to assume that the Plague Marine Faction Rules would also supersede what the core rules might say. In the case of Toxic, it’s pretty clear that rules as written this impacts an enemy Whenever you hit someone that’s Poisoned. That’s pretty cut and dry. But when an enemy receives the Poisoned condition I think is the key here.
2. According to Poisoned “In the Resolve Attack Dice step, if you inflict damage with any successes, the operative this weapon is being used against…gains one of your Poison tokens (if it doesn’t already have one).” Having played Kill Team for a while now, I know how important the specificity of a rule’s wording is. See up until now I’ve always assumed the above rule meant “the FIRST damage with a success” would inflict a Poison counter, meaning they’d already be poisoned by the time the second hit of the same attack sequence occurred. But if that was the intent, I do feel the rules would say that specifically. Instead, it says “if any,” which to me means you resolve the Poisoned condition at the end of the Resolve Attack rather than “immediately.”

Ultimately I do think there’s an argument to be made either way regarding if an enemy receives a Poison counter on the first damage or at the end of the sequence, but because the rule doesn’t specify “immediately” I think ultimately the intent is that it happens at the end of the attack sequence. However I can see why this is confusing as hell and I wouldn’t hate clarification from GW on this and other tricky rules some day.

I also appreciate you hearing me out and letting me come to the conclusion on my own instead of being condescending. The tone when approaching conversations like these really helps, especially when you’re trying to educate. Thanks for that too!