I used nothing the beat it, S Rank. Here's some tips: look at its pose. Its pose can tell you about an upcoming attack. If you see it's preparing to launch an attack retreat your line to somewhere safe by dragging it or just lift your stylus. About the toxic cloud, just make slow and steady circle. It won't move so feel free to slowly encircle it, then speed up when the cloud disappears. If you think you can't make too many circling when Drapion is using the toxic cloud, just make one circle at a time to keep the Friend Gauge from draining.