Basically, as this is panning out in my mind with the current argumentation, on Achilles's side of things, he's a skilled combatant that could basically oneshot by sneezing on Yanagi, and he leads with pistols, giving him range advantage, only resorting to swordplay as a last resort. On Yanagi's side, he has the skill advantage, which helps counter Achilles's AP advantage to a degree (less likely to be hit), he has Benda to negate durability and eat away at Achilles's pain tolernace, Poison Hand to slowly eat away at Achilles. Achilles resists Poison, which gives him more time to deliver that 1 golden hit to kill Yanagi, but on the other side of things, the longer Achilles takes to get that hit, the less likely it'll be, what with him getting both his vitality diminished via Poison and his pain tolerance diminished via Benda. Finally, Vacuum Palm, the riskiest move of this fight. Achilles is wise, so the arguement could be made that he's wise enough to ignore Yanagi and take his shot, killing Yanagi (though he'd have no way of knowing one hit would be the end of it), but the argument could equally be made that Achilles is wise enough to listen. Yanagi might be about to give away an important detail about his power or motives or whatever the case, making the ever cautious Achilles keep his guard up, but listen for a detail to allow him to exploit a weakness. Yanagi, finishing his shpeel, gets closer, at which point Achilles would either try to put a bullet in him if he had ammunition left or cleave him in 2 if not, giving Yanagi the chance to dodge in and oneshot. I believe this would likely only play out this way if Yanagi infects Achilles with his Poison Hand and Achilles realizes he's been poisoned, as if Yanagi starts talking about "The Most Poisonous Gas", Achilles may come to the conclusion that Yanagi poisoned him and that if he gets enough information about the poison, he can retreat somewhere into Sanctuary to hide, synthesize an antidote, and use his stealth mastery to ambush Yanagi, not only getting rid of his disadvantage, but gaining an advantage in the process.