>>36983862>rock slide70% Acc Hustle Rock Slide + Adamant nature does OHKO, but it still depends completely on it landing and having every possible advantage (max IV's and EV's). Swarm can't OHKO.
On the other hand, any Special Fire Type move above 40BP completely decimates Durant even without any investments and detrimental natures. Fire Lash does need a neutral nature (but no investments) for it to OHKO.