One of the sillier criticisms of Hell is that it is a scare tactic. Fear is a great way to manipulate people, and so atheists especially suggest that Hell was merely invented as a way to coerce people into believing the Bible. There are a great many problems with this criticism, starting with the fact that in order to fear something, you must first believe it exists. Only a lunatic tries to hold up a bank with a pink plastic water pistol.
Of course, although Hell is an element of the Christian faith, few Christians will include it in their list of reasons they converted. That's not to say you won't find anyone professing faith for fear of Hell, but if you ask people "why are you a Christian", you're very unlikely to get the answer "because I don't want to go to Hell". Christianity is a well-evidenced faith that appeals to both the mind and the spirit. Yes, the threat of Hell is there, just as the threat of prison is there for those who refuse to abide by the law, but it is not a large part of why people become Christians.
But let's suppose it was. Let's imagine a large portion of people become Christians because they fear Hell. Would that affect its truth value? Certainly not! If Hell exists, it exists in spite of the fact that it's scary. If it doesn't exist, the fact that it's scary isn't the reason.
To illustrate this, consider the scene to the right of this paragraph. Here, you see a scene from Jurassic Park, a 1993 movie in which a company by the name of InGen resurrects dinosaurs for a theme park. The park is sabotaged, allowing the dinosaurs, including the 12ft t-rex, to escape their enclosures. In this scene, the t-rex has knocked down a wooden toilet shed, revealing a very terrified Donald Gennaro, whom she promptly eats.
Now, I don't know about you, but I'd be rather frightened if a gargantuan reptile demolished my cubicle and stared down at me with hungry eyes. Nevertheless, if people were running around saying Jurassic Park is a true story, my response wouldn't be "well that's scary, it can't be true". There are a number of better arguments against the reality of Jurassic Park.
Not only is "it's scary" a stupid argument against the existence of Hell, but Christians, and indeed other believers in an afterlife, could make a similar argument. Hell may well be a scary concept for an afterlife, but so is the thought that there is no afterlife. It is said that the afterlife is just a pleasant lie for those too afraid to accept their own mortality. But if Heaven is just a pleasant lie for those who are afraid to accept their own mortality, could the rejection of Hell, by the same reasoning, not be a lie for those afraid to accept that wrath is owed for sin?
Do you see how appealing to one's motives for holding certain beliefs (which is an argument known as the "genetic fallacy") has absolutely no effect on the truth thereof? If there is a Hell, it exists in spite of the fact it is scary. If there was no Hell, the reason it didn't exist would not be because it's scary.
The reason we know Hell exists is because we have been told it exists by the one man who has ever conquered death. Jesus Christ, God in flesh, died by crucifixion, was laid in a tomb, and on the third day, He got up and walked. Even before this great feat, He demonstrated His command over nature, sickness, demons, even death, through a range of irreplicable miracles and exorcisms, using only His own commands. I'm willing to lay this down as a rule: It is far better to listen to the man who rose from His grave than 8 billion who are heading to theirs. Not only does Jesus tell us that Hell exists, but He also tells us that by confessing Him as Lord, and believing He rose from the dead, we will be saved.
And that is the glorious truth. Christianity isn't a message of fear, but of hope. It isn't "believe, or you'll go to Hell", it's "believe, and you will receive the free gift of eternal life". Hell is not a scare tactic, but a fact. From the very first sin, it is decided that we will go there to be justly punished. But salvation comes from Christ, who was punished in our stead, not out of hatred, but of love. If you want to turn down salvation because you hate the thing you're being saved from, all I can say is you're as irrational as a man who will willingly drown because he's scared to grab the lifeguard.