By far one of the most slept on rappers in the game. He's been around since 1995 and has 7 albums, the most recent being Book of Ryan at the time of writing. He is most well known as one half of the duo
Bad Meets Evil with Eminem. Dre almost signed him to Aftermath, and he wrote a couple of songs for 2001. He used to have beef with
D12 until shortly before Proof was killed in 2006. Since then he has released
Hell: The Sequel with Eminem as well as a few other collaborations. He seems to be getting a little more recognition recently though with his most recent 2 albums Layers (2016) and Book of Ryan (2018). In my opinion he is one of the only emcees alive who can outdo Eminem on a track.