Ben 10 Omniverse

Each transformation requires two level ups, at 2000 experience a piece. so each transformation requires 4000 exp, with 13 different transofrmations this means the total amount of XP required is 52000. This may seem like a large number, but i managed to get this in the level 'Plumb Crazy' towards the beginning of the level. This was without trying to avoid fights so with fights you can avoid it should be easy enough to get by the storylines completion. If you dont just replay the level Weird Scientist and use Graavattack whenever there is space to and push the enemeies off of the edge (RT+X).