We had potential to be monumental, 'ville mentality
You know that old kill or be killed mentality
I look at where you at now it's a, real fatality
The friend cole is talking to had the potential to be succesful. He knew that he didn’t had all the time of the world, and he could be killed mentally. The friend has failled fatally. Going with the drugs doesn’t really help that.
In other words, Cole is saying this friend had the potential to achieve the same level of success he is now enjoying. This potential stemmed from the mentality that their hometown taught them which was that you either had to kill (probably a metaphor for grind for success) or be killed (be left in the “ville”, or Fayetteville).
He then goes on to reflect on how this friend never fulfilled this potential and is now at such a low place that he has been ‘killed’, a reference to the last line, saying that since he didn’t work for success he has been left in the ville.
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