My first thought was a Quagsire from behind, but that would be more of a dark teal than purple (and also the official artwork shows it from the front). I'm thinking maybe Suicune?
Actually rereading it now I realize it was missleading in my previous post. I will give the point to BZ because it was Quagsire ' The little purple bit on its back/side. Here is your next target:
Nice one guys, I hadn't realized how much Solgaleo's foot looked like a tire until I took that snapshot. Here is your next target: