To earn this achievement, win 5 battles in a row without losing a battle in between.
I just followed the quests and some required me to win battles. I played a mix of campaign and PVP battles and still unlocked it.
You might be able to earn this by playing mission 1 of the campaign and winning 5 times in a row, but I do not know. If this works for someone, leave a comment.[EDIT: Loonielee confirmed in the comments that playing 1 campaign mission 5 times in a row works.]