Kha'zix is one of the best mid laners in the game if played right, you max W for harass and zoning.
You evolve W first so you can zone more and deal more damage.
You max Q after you are done with your W and the next evolve should be your E.
If you play kha'zix mid you should rush Boots of lucidity, tears of goddes and brutalizer for sustain, cdr and armor pen.
Mid/Late game you go Black cleaver, Muramana, bloodthirster, Guardian angel, last whisper.

EDIT: Kha'zix is not the greatest toplaner and he is a slow jungler with poor gank ability.
If you get Kha'zix mid in Soloqueue thats free elo.


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