There’s the atheist joke that “Christians are announcing that without belief in Hell, they would be horrible people” or something to that effect.
Sad thing is that there indeed is truth to it, and it has consequences. As much as I dislike organized religion and on practical level, would align with scientific, materialist worldview, I do think that without straight forward “be good or be punished” paradigm, a lot of people will be exactly the kind of self-centered assholes we currently see in positions of power in the world.
Back in the day, rich people would fund hospitals and schools in hopes of getting to heaven. These days why bother, religion is mostly a cultural artifact to occasionally pay some lipservice to, while one fully believes that their material possessions are all they got, and even their lowest possible pleasures should be attended to with whatever resource they can spare. Scientific materialism helped get rid of a lot of assbackwards reasoning but with cold hard logic, came the ease of reducing everything to a number. Money, usually. Worth. Nothing else matters. You can’t put a number on love, care, kindness, or something as ephemeral as “goodness” - an ever moving target which is only ever defined by the person using the word, with luck at least slightly informed by (pro-)social contracts. Indeed most people would specifically reject any attempt to put a number on those qualities as it would run counter to their virtuous nature. Which just makes it easier for those with power to devalue those qualities entirely, and with power, build structures that lets them indefinitely get away with it.


No, they don’t need Hell. Christianity is used as justification for all sorts of nightmarish crimes against humanity; as is Islam, Judaism, et al.
Also, don’t forget, the Bible/Tanakh/Koran teaches that murder is okay, as long as God tells you to do it; so when a woman drowns her children in the bathtub, she thinks it’s for the best! “They won’t be stuck on Earth to suffer, and will fly around Heaven with little wings”.
Putting Abrahamic faiths to the side (a very common justification for terror), those without the faith do the same thing; they justify what they are doing to themselves.