Farigiraf
Farigiraf's Armor Tail blocks all priority aimed at it — including your Fake Out and Extreme Speed — so it sets Trick Room unmolested. Under Trick Room its middling 60 Speed becomes an asset, and Sap Sipper means Grass moves and Spore-style tactics feed it instead of stopping it.
Don't Fake Out the Farigiraf to stop the Trick Room — Armor Tail makes it immune to priority, so your Fake Out whiffs and you lose the turn. Don't throw a Grass move at it either: Sap Sipper absorbs it and hands it a +1 Attack.
Taunt stops Trick Room before it goes up. It has to land before Farigiraf moves, so pair it with a faster turn or Tailwind — but a Taunted Farigiraf is just a bulky attacker with no setup.
Kingambit's Dark STAB is super-effective and Kowtow Cleave ignores the target's evasion/redirection concerns; Supreme Overlord makes it hit harder as the game goes. It doesn't care about Armor Tail because it's clicking a damaging STAB, not priority.
Dark STAB is super-effective into Psychic, Levitate dodges Ground partners, and Snarl lowers Farigiraf's Special Attack so its Hyper Voice/Psychic stops threatening your side while you set your own pace.
Farigiraf sets the room for a slow partner (think a low-Speed heavy hitter) that then cleans up while you're forced to move last. Removing the room with Taunt is often better than KOing Farigiraf, because the partner is the actual win condition.
Every answer on this card was checked against the live learnset and roster data shown above — a citation that no longer holds is dropped, not shown. Type-based answers are computed from base stats and STAB. Speed is the real level-50 maximum. This is deterministic and sourced — no guesses.