Triumph: One-shotted Steven's Metagross with a Vulpix.
Failure: So used to Battle Spot Singles that when I was battling in a Link Battle, I forgot that it was not in the Battle Spot and accidentally only picked three Pokes to enter instead of six. I lost, big-time.
That Goodra may have 399 Special Defense and an Assault Vest, but I'm pretty sure it couldn't stand up to 6 Pokes in a row.