Use water, ground, or rock attacks.
A good Pokemon to use would be your mudkip/marshstomp/swampert, but if you didn't start with mudkip then azumarill is a good pick. It has some pretty decent water attacks and rollout is very effective.
beat the 4 gym beat the 4 gym
You try and beat the 4 th gym
after you beat the 4 gym leader in hearthome city
after you beat 4 to 5 gym leaders you can face him
go back to your fathers gym and defeat him
get some fighting types
you have to beat 4 other gym leaders
You go to fight your dad as the 5th gym leader in Petalburg city. This happens after you beat the first 4 gym leaders.
You have to beat 16 gym leaders and beat elite 4 in kanto and johto to beat the game.
Beat 4 Gym leaders then beat the gym leader in petalburg city.
if ur talking about petelburg gym, it wont as long as you have 4 badges
beat the gym