This guy is far from invincible. For one thing, you gave it a Choice Band for some random reason. Now does that make any sense whatsoever? Why would you need to increase your Attack stat when your foe is only going to have 1 HP after using Endeavor? Plus, using a Choice Band would also mean that you can't even use the FEAR strategy, as you would be stuck using one move. It even makes you more of a target for Struggle with Torment. Multi-hit moves will destroy this Pokemon, as Sturdy only activates for the first hit in a multi-hit move. Destiny Bond would also take this guy down. A foe could use Gastro Acid, Skill Swap, Worry Seed, or Entrainment to remove your Sturdy. Giving you an item like Ring Target, Sticky Barbs, and Life Orb could take it down. The foe could use Soak to remove your type and then take you down with Sand, Poison, and Burn, or use hail to take you down. Also, a foe with Rough Skin, Iron Barbs, or a Rocky Helmet can take you down. Confusion can also defeat this Pokemon.