Anyone who wants to which means anyone who doesn't want to go to Heaven. But understand that wanting to go to Heaven means loving God because God is Heaven. It's not just the desire to be saved or to have a beautiful afterlife surrounded by your loved ones or whatever it might be. It is loving God, your Creator. So, who goes to hell is anyone who doesn't love God.
Let me explain what I mean by this. I don't see hell as just a place of darkness or fire or cold or whatever it might be, somewhere you are constantly tortured by demons with pitchforks. That may be an extreme version but hell could also be a place of utter banality. There are probably different hells of different degrees of separation from God that are created by the mindsets of those who go there and so reflect different mentalities. There may be hells corresponding to the various vices as in Dante or there may be intellectual hells where clever materialistic atheists go. They won't exactly suffer but they won't know the joys of Heaven and, unless they repent and turn to their Maker, they will start to shrivel up spiritually which means their consciousness and sensitivity to life will gradually attenuate, becoming less and less responsive. They will fade not blossom.
Those who go to hell are not necessarily bad people as the world sees bad. They are spiritually unresponsive in one way or another but they are not necessarily wicked or evil. They have just failed the greatest lesson of life which is to love God. Clearly, none of us loves God as we should but even wanting to love God is enough for him to work with.