KINGDOM HEARTS HD 2.8 Final Chapter Prologue

Don't worry about this achievement. It's almost unmissable. I actually think it might be, if you finish the story. Before Sora goes to the Pinnochio world, he is told to do a drop in which he just has to pop 150 balloons. Simply pop those balloons, get the ring to exit, and you're golden. I didn't see any enemies in this entire drop, so it was impossible to get hit.