I assume you are not talking about legendary dragon types so I will talk about non-legendarys.
Salemence is a good option because it has a high Sp. Attack.
Garchomp has a decent speed and a large movepool.
Dragonite has large defences and can improve it's Attack and Speed with Dragon Dance.
Kingdra has only one weakness: dragon moves and can also use Dragon Dance. It has a small movepool so that makes it less effective. You could try to use Rain Dance to activate it's ability: Swift Swim which boosts it's speed.
But if you wanted to fight a dragon type, wouldn't ice be a better option?
Source: Looking at stats, Experience and The Internet.