Dragonair
Dragonair is the evolution of Dratini and can be found only in the Dragon's Den. In the Dragon's Den, you will need to use the "Super Rod" in any body of water to have a chance at encountering Dragonair. Because Dragonair only has a 3 percent encounter rate, you may be using the "Super Rod" several times before you encounter a Dragonair. Additionally, if you do not wish to catch a Dragonair and simply wish to battle one, you can challenge any trainer in the Blackthorn Gym.
Strengths
Because Dragonair is a Dragon-type, it is strong against practically all other types in the game. Dragon-type attacks are only super-effective against other Dragon-type Pokemon, but because the Dragon-type attacks are usually extremely powerful, they will still cause a lot of damage. The only type of Pokemon that Dragon-type attacks are not very effective against are Steel-type Pokemon. Consider using a Steel-type Pokemon such as a Metagross or Steelix to minimize the damage caused by Dragonair's attacks.
Weaknesses
Like all other Dragon-type Pokemon, Dragonair is weak to only two types of attacks: Ice-type attacks and other Dragon-type attacks. For this reason, focus on using Ice-type attacks such as Blizzard or Icebeam to weaken Dragonair. Do not use Fire-type, Water-type, Electric-type or Grass-type attacks, as Dragonair is resistant to all of them. Because of these weaknesses and resistances, it is best to use a Steel-type Pokemon that knows an Ice-type attack.
Strategy
Because of Dragonair's "Shed Skin" ability, paralyzing it or putting it to sleep is not an option as it will simply heal itself the next turn. The idea is to use strong, physical, Ice-type attacks as Dragonair has both a low defense and low HP. Ice Punch or Ice Fang are good attacks to use against a Dragonair. Avoid using any of the four types that Dragonair is resistant to.