I was going through my polish trying to find a beauty I haven't worn in a while that is spectacular on its own and my Mac Formidable! jumped out at me. It is from the Venomous Villains launch and sold out very quickly. You can see why in the pic.
Formidable! has a deep plum base that shimmers teal, blue, violet, and fuchsia, depending on the light. I am not a fan of the base color though I love the duochrome aspect of it. The quality isn't all that great as it chips easily within the first 2 days. I'll probably change it by then. It is a dead on dupe for Orly Galaxy Girl which is much cheaper and easily found. Anyways, check out how awesome it looks.