This achievement seems really hard, and as you try for it you'll get hit at least once almost every time. You might be lucky to get 1 perfect every 10 battles. Using the Deadly Nadder tactic, with practice, you should be getting perfect 9 out of 10 times. I have made a video of me getting 3 in a row to show you how easy it is! I found going against the Nightshade dragon was easiest. Default dragon editor edition of course, while you use your overpowered Deadly Nadder from the story. I have tried all of the legendary versions, and their points are not distributed well! You cannot be hit even once. It doesn't matter if you're life refills, you will not get a perfect if you're hit.