Short answer: Any level.
Long answer: The evolution of buneary isn't tied to its level, but its happiness. You can raise happiness by having the Pokemon in your party (one point evers 256 steps), levelling it up, taking it to a massage in Veilstone City, and giving it berries that say they raise happiness, and probably other things I forget.
At some point in the game you get a Hapiness checker for your Pokétch; if you touch the little Sprite of the buneary on that, and two hearts pop up and then grow big, the hapiness is maxed out, and it will evolve the next time its levelled up. (I'm not sure it needs to be actually maxed or just close to it, but maxed works.)
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To evolve Buneary into Lopunny u need friend ship worked for me! =3 So try battiling with it not fainting or whatever and level it up and it will evolve 2nd Answer: Buneary evolves by happiness, For instance, if u have a togepi (u can get one from cynthia) You evolve the togepi by leveling it up, feeding it poffins, massaging it, and it will evolve to togetic. Same with Buneary. Hope this helps :D
buneary evolves by friendshipMake it level up with a high 'friendship level' to evolve.
Pachirisu does not evolve :(
Buneary evolves when its friendship with you is high enough and i advise y6ou to level it up to a high level then with friendship it will evolve
Level 10