100% of sinners have no excuse for rejecting faith in God as revealed per Rom. 1:20.
There are two main ways God/Christ is revealed:
1. General revelation, which includes meditating on the natural world or God’s supernatural work and moral conscience. Paul said men are without excuse, both because God’s eternal power and divine nature (love) are manifested by creation (Rom. 1:20), and because
a proto-gospel has been proclaimed to everyone under heaven implicitly or in pre-NT foreshadowings (Col. 1:23, Rom. 10:13-18, Gal. 3:8). He also taught that all normal humans have an inner
conscience or “common” sense (Rom. 2:14-16), which manifests morality or a moral Authority in every culture, beginning with the Golden Rule (Matt. 7:12).
2. Special revelation (1Pet. 1:8-12), which refers mainly to divinely inspired NT teaching regarding God’s history of salvation. Again, the
Parable of the Talents indicates that souls are saved via faith in God/ Christ as revealed (cf. 1Cor. 10:1-5). Truthseekers around the world in all times are pilgrims at various places along the road of life, and all true roads eventually lead to the Way to eternal life in heaven (John 14:6, Acts 24:14, Phil. 2:10-11). All truth leads to One Way.
Re hell:
MFW/moral accountability only exists when there is the possibility of choosing between two qualitatively opposite moral options that we call good and evil. These options are opposites because of essentially different consequences for choosing them. Choosing good results in blessing, life and heaven; and choosing evil results in cursing, death and hell (Deut. 30:19). This is why hell as well as heaven exists. It is the just consequence for choosing evil rather than God. The Spirit of God is good: love, peace and joy (Gal. 5:22-23). Therefore, whoever rejects the Lord is spiritually separated from Him (Isa. 59:2) and thereby chooses the evil or satanic spirit of hatred, strife and misery and reaps the just consequence called “hell” in the afterlife (Gal. 6:7-9, Heb. 9:27-28).
Evil people punish/torture themselves by experiencing delayed karma, just as those who experience appropriate justice during this earthly existence also punish themselves or reap what they have sown and send themselves to jail. This view makes souls responsible for breaking the rules rather than blaming evil on the judges (or Judge) who enforce the rules. The purpose of earthly punishment is to promote repentance, but the reason for retribution in hell is to attain justice. It is difficult to imagine, but somehow even someone as evil as Hitler will receive perfect justice, perhaps experiencing the agony of the millions of deaths he caused in accordance with the principal of “eye for eye” (Matt. 5:38).
After justice is attained atheist souls are destroyed forever (per John 17:12, Rom. 9:22, Gal. 6:8, Phil. 3:19, 2Thes. 1:9, 2Pet. 3:7 & Rev. 20:13-14).
Hope this helps you put the O and N together better.