Ivysaur is the even eviller evolution of Blubbersore. The bulb on its back finally blossoms into a flower.
It loses its man-eating properties in exchange for pollen that is full of delicious nutritious neurotoxin. Its appearance changes by blossoming the flower, and growing dark triangles like all dinosaurs. It's also a little bigger than Bulbasaur. It then gets evicted by its landlord and is forced to move into the dodgy part of the jungle that is full of more dangerous bugs and man-eating plants.
Its strengths and weaknesses don't change at all, so see the Bulbasaur page for more info. The only difference is it's stronger and loves people who have severe pollen allergies.
It evolves into the Mighty Venusaur, and believe me, it gets even EVILLER!!!