I actually believe the NT is the Word of God written.
Therein, Jesus is the one who gives the most warnings about hell.
But please keep in mind there is a difference between the 'Bible hell' and the concept of it from 'Pagan hell' teachings and beliefs.
The Pagan hell torture developed from ancient pagan Babylon.
The Bible hell [the hell of Jesus teachings] comes from the old Hebrew Scriptures. [Sheol]
Jesus was buried in the Bible hell until God resurrected him. -Acts 2vs27,32.
Because Jesus taught the dead are in a sleep-like state, [John 11vs11-14] then Jesus would have believed he and those in hell would not be in torture, and not be conscious of anything until resurrected from hell.
[Rev 20vs13,14; Psalm 6v5; 13v3; 115v17; 146v4; Ecc 9v5]
So, the Bible hell is mankind's stone-cold common grave of mankind.
'Gehenna' is another word that ended up translated as hellfire.
Gehenna was Jerusalem's garbage dump where things were destroyed.
Nothing was kept burning forever in it.
So, the Biblical hellfire [Gehenna] Jesus was using as a fitting symbol of destruction. Destruction is also for Satan according to Hebrews 2v14 B.
It wasn't until after first-century Christianity ended that the pagan hell concept or idea became mixed into religious teachings by the clergy class.
-Acts 20vs29,30