Enitie is fire type, so most of th neat balls don't help you. You need a fast pokemon with mean look or a similar move/ability so he can't run and then you can wear him down. When it has low enough HP, you could try to use ultra or dark balls (if at night, which I recommend) If you don't want to go through the trouble, just use your master ball. And of course, save before you try to find it.
It is hard! You need a lot of balls on you, but try not to give up!