I would not have guessed Mykah N9ne. I think he is up there, but that the sample size is too small. I am almost certain that MC Paul Barman and maybe MF DOOM have a larger vocabulary. There are also guys with less recorded or accesible material like Sesquipidelian and Divine Styler and Dose One. My Money is on MC Paul Barman, though: https://www.youtube.com/watch?v=thABL7wiS0M
So you can go to Yandex and just click on videos without searching anything and it'll list a lot of the most popular videos and things that you can just watch.
