I don't really hate MegaVenusaur design, is just that I find the front part of the plant in his back kind of hollow.
After adding a leaf with my half-assed paint skills, I came to the conclusion that while it looks a lot better this way, is basically a bigger version of Venusaur without almost anything different from its predecessor. Maybe Gamefreak got frustrated over the idea of improving Venusaur forcing them to add a ridiculous pink shower hat.
Gamefreak should have came with better ideas, I still can't figure out how to improve Venusaur without giving him inecessary details, the flower in his back looks kind of artificial right now.