During my first run of Reborn, I swept Julia with a Mightyena with moxie and then Mightyena fainted after finishing off the last pokemon. Felt like such a dramatic way to go....luckily this wasn't a nuzlocke.
Ruining Ditto Arceus's accuracy with prankster Purrloin and then proceeding to utterly destroy it with my Scrafty during my mono dark run.
Setting Shelly's gym on fire with my shiny Growlithe and destroying her team as Growlithe gets stronger due to flash fire.
Like Shelly, Noel got swept by my Typhlosion after burning the field and then spamming Eruption while flash fire gives it a boost.
Beating Kiki on the first try with my mono dark team.