This is probably the hardest achievement in the game! The battles are now way more intense and you have to beat 4 dragons in a row without having one KO against you. At first I was having problems with this, but then I figured out how to be extremely cheap and make everything really easy. Use Deadly Nadder as a dragon (hopefully you picked this one up like suggested). Make sure it’s a level 22 (the highest you can be doing all the trainings and challenges). Use the method you've probably been using this whole time anyways described in the roadmap, or refer to the "Perfect" achievement which shows a video on the tactic. This will prove difficult otherwise, unless you are very good at the game. Save after every win!