One Hit KO Deaths

When running a Pokémon Challenge or Nuzlocke, there are sometimes unexpected things that happen. One of them in particular may be a One Hit KO death. This happens when you know your team is strong enough to beat your opponent, but one of your most loved Pokémon member on your team dies unexpectedly due to a one hit KO move like Sheer Cold, Horn Drill, Guillotine, Fissure, or in some cases, a critical hit. Have you ever had an experience in which one of your Pokémon in your challenge died because of one of these moves? How did it affect the rest of your challenge?