I can top this. Battled a guy earlier (referenced it as well) he was good, but my some of these tactical Errors.
Let's see:
Paralyzed a Ferrothorn making it's Speed drop Lower, making Gyro Ball a little stronger. Kept swicthing out constantly with Stealth Rocks on his field (His Chandalure almost fainted from that alone), KOed my Gimmick Zygarde with Burn Damage yet on the same turn still used Phantom Force, letting me switch into Ferrothorn and great his Gourgeist with a Iron Barbs + Rocky Helmet Physucal Wall when PF hit. When we was down to last Pokemon (a Milotic) and i had two (my Gengar and Delphx) he preceded to KO my Gengar instead of letting Burn Damage take it out, and lost by Destiny Bond. He would have won not for that one. (And no I wasn't using Mega Gengar, I used Mega Blastiose).