For this achievement you have to win 3 ranked duels in a row. A ranked win will NOT count if your opponent quits / forfeits before their 4th turn. If YOU quit before your fourth turn it still counts as a loss so this is difficult to try to boost. There is no easy way around this, just play aggressive and play your best. I would suggest going for this achievement fairly early as the game is supposed to be pairing up players of equal skill and it will be easier beating new players than veterans who have had time to build up their decks.