We have to rank the sin and explain why we put them there.
Can you give me example you would add to hell?
In today's society the levels of hell would be added to Dante's hell or modify. For example where would you rank a pedophile?
In Dante's time, terrorism did not exist (at least not in the form in which it exists today). Crimes of terrorism could be added to a hierarchy of sins and given a special place within the larger category of murder.
Of course, terrorism is a complex term and the behaviors the term describes are varied. Acts of terrorism that we can all agree fit into the definition of the term include using bombs to destroy non-military facilities like the World Trade Center, subway trains and markets. These events also kill innocent people.
The non-military and arbitrary nature of terrorism targets makes this kind of act especially cruel and thus can be argued to be a greater crime than killing out of a pointed anger or killing an enemy that has caused previous harm. The fact is that this mode of selecting targets has an intended effect - to frighten and terrorize whole populations. In addition to destroying lives, terrorist acts like the bombing of the World Trade Center undermine the public's confidence in their own safety.
A "beastly sign of hate" seems apt for placing this type of behavior among Dante's lower circles.
On a different note, there are now corporate and/or white collar crimes that did not exist in Dante's day. The Ponzi schemes and investment gaming that have been so damaging to people's lives (and carried out by people who are often not prosecuted) are easy to document. The crash of 2007/2008 was not entirely criminal, but it was driven by behavior that has been described as criminal and which, in some cases, was definitively criminal. Placing such a crime in Dante's scheme would be a challenge. Although, thieves and swindlers have a place in Dante's hell.
In addition to the obvious that some have mentioned above, I would also have racists, bigots and spiteful/mean-spirited people.
People promoting hatred of others based on race, religion, sexual orientation, nationality. etc., would be in my version of hell. I'm afraid that would put many people in hell who assume they are going to heaven...
Murderers, thieves, cheaters, drug pushers, prostitutes...that's just a start. What else do you think belongs there?
One way to approach this is to look at a map of Dante's Hell and think of more modern crimes that match the crimes of that time. For example this map is pretty good. Once you are familar with the map, think of today's world values crimes differently. Is being a traitor still the worst thing in today's society?
Then, once you have the order established, think of modern-day versions. For example, in the Violence area you could have "road rage".