According to scripture can an atheist fully disbelieve in God?

The scripture does say that a person can deny the existence of God in their hearts, which I take to mean a ‘sincere disbelief’ not just the claim of disbelief: > 14 The fool says in his heart, “There is no God.” > They are corrupt, they do abominable deeds; > there is none who does good. (Psalm 14 ESV) However, in many other places of scripture, it seems to declare that God’s basic nature is declared in a self-evident way. - Therefore is there such a thing as a real ‘pure atheist’ or is that just an imaginary person? - Is there anything in scripture that clarifies the tension between self-evident truth and the fool’s ability to deny that evidence? - To what degree is the denial possible? - Is there even such a thing as a real atheist?