For which types of people does Allah mention Eternal Hell? Are they those who are clear enemies of God and mankind such as Athiests ( purposely denial) and dictators who have committed mass opression?

We can conclude that those who are stubborn and arrogant, and they defy God, are the ones who will dwell in Hell for eternity. These people try to defy God even on the Day of Judgment. If God brings them back to this world, they would again pursue corruption and deviation. As for other people, Allah will forgive them and they will be freed from Hell. Most people who enter Hell will be released from it.