If we were to get technical, Swellow has everything it needs to take down everything bar Steel Types.
Ability? Check! Guts doubles Attack when Poisoned, Burned or Paralyzed.
Moves? Check! Pursuit deals with Ghosts, Facade doubles in Power (To 140 not including Same Type Attack Bonus) when Poisoned, Burned or Paralyzed, Protect can buy it an extra turn, U-Turn for when things get bad, Brave Bird.. (140 Power Move without calculating S.T.A.B)
Items? Check! Flame Orb/Toxic Orb - Free Burn/Poison.
Protect, Get poisoned/burned, flip shit with a Pokemon that has about 600+ Attack and high power moves. Ampharos wouldn't even get a hit in before being 'Knocked the Fuck Out'.
Edit: Reading back on this, I now realise how much of a nerd I am when it comes to these games.. Still regret nothing though