Nocturne vs Teemo Counter Pick

Blinding Dart is a hard counter to a champion whose passive lives on basic attacks. Umbra Blades strikes surrounding enemies and heals Nocturne every few seconds, its cooldown falls as he attacks, and a blind stops all of it for the duration. That is the mechanical core of a 46.2% result over 208 games played on patch 16.13.1: Nocturne loses, though the sample is modest enough that the exact figure should be treated as approximate.

The rest is positioning. Guerrilla Warfare turns Teemo invisible if he stands still and takes no action, so first contact often happens on his terms rather than after a Paranoia leap. Noxious Trap scatters mushrooms that poison and slow, taxing the pathing of an opponent who moves at 345 and wants to arrive quickly. Toxic Shot poisons on every attack for four seconds after impact, and combined with the dart that makes his profile mixed, so 38 base armor covers only part of the threat. Where Nocturne wins is contact: 655 base health against 615, 62 base attack damage against 54, and Unspeakable Horror fearing Teemo if he cannot clear its range, which at 330 move speed is difficult once a Dusk Trail is down. Blocking the dart with Shroud of Darkness is the single highest-value use of that ability. Details on the Teemo page.