The first thing I'd probably say to him would be this: Why gamble with your soul? After all, that's exactly what your friend is doing. He's betting first of all that the Bible is wrong when it tells us that someday all the evil and injustice and corruption of this world will be judged. To put it another way, he's betting that God doesn't care about right and wrong, and that people who have done terrible things won't ever be punished for their evil deeds.
But he's also betting that it won't make any difference if he goes through life ignoring God and living any way he wants to. But Jesus warned, "What good will it be for a man if he gains the whole world, yet forfeits his soul? Or what can a man give in exchange for his soul?" (Matthew 16:26). He may be surprised to learn that Jesus spoke about the reality of hell more than anything else in the Bible.
The greatest truth about hell, however, is this: We don't have to go there! Only one thing will banish us from God's presence forever -- and that is our sin. But when He died on the cross, Christ took upon Himself the judgment and hell that we deserve. Put your faith and trust in Him for your eternal salvation -- and then urge your friend to do so, as well.