This is survival of the fittest
In simple “all-out brawl” terms, it means Em is challenging every other rapper, such that only the best rapper will still have a career after this is over.
However, with the idea of natural selection in mind, it is reference to the animal kingdom’s need to adapt to the environment in order to keep up with competition so that they survive. It parallels with the rap industry where only those who have talent and skill are the ones who will continue to thrive and become successful whereas the weaker artists quickly die out.
Matches very well with the animal references later in verse one, even more with the ruffling feathers line.
To help improve the meaning of these lyrics, visit “Survival” by Eminem (Ft. Liz Rodrigues) Lyrics and leave a comment on the lyrics box