I said Taliban.
The reason for this is that while bad, I think the Nazis have been greatly exagerrated by propaganda during the war. As I've mentioned before, we know that things like human flesh lampshades, and portable bone grinding machines were complete lies intended to demonize the enemy, a good thing to do in a time of war.
The Nazis were a bigger threat because they had the power, resources, and popularity to make a pretty solid bid for world domination, and came extremely close to success.
I however think The Taliban is "worse" because while not as powerful in an overt sense as the Nazis were, their objectives are much scarier in the end. The Nazis wanted to conquer the world and annihilate two groups of people: Jews and Gypsies. The Taliban wants to pretty much kill or enslave everyone other than themselves. Where the Nazis were more or less driven by reason (even in some of the occult motivations), The Taliban are beyond reason since they are fighting based on faith.
What's more, few people take the threat posed seriously, which is why they haven't been demonized, and why instead of fighting a real war to deal with the problem, we have instead engaged in a sort of ongoing occupation/police action.
While a lot of people don't like what I think on the subject, I will also say that I think the problem is the culture of the region in general. "The Taliban", "Al Queda", and other groups are just the flavor of the week. We're not dealing with a fringe element in the region, but with the majority, even if most do not actively fight. The problem with engaging something like "The Taliban" is that those "poor oppressed people" actually aid the enemy en-masse and are willing to literally sacrifice themselves to protect Taliban fighters. According to reports I've read in both Iraq and Afghanistan one of the problems with ambushes is that you'll have enemy fighters approach in crowds of people, fire an RPG at a jeep or something, and then hit or miss flee, with the crowd litterally closing around them so that American troops won't return fire due to the "civilians" and if any of those people are hurt a big deal is made out of it which hampers out efforts due to liberal outcry, people will pay more attention to the "poor unarmed civilians, gunned down by soldiers" than the flaming jeep and dead US/allied troops.
The Nazis represented an overt threat we were mentally and morally prepared to face. Soldiers, armies, and a clear enough threat where we were able to control information enough where we didn't have backlash when our troops did what was nessicary against groups like the Hitler Youth and Volkssturm. To beat groups like The Taliban, we need to pretty much realize that our morality in how to engage in warfare against who is wrong, despite how deeply engrained it is. When I (and on other sites, other people) talk about waging a "total war" either on the entire region, or specific countries we are involved in, people immediatly freak since a lot of it matches what people have been taught to consider Genocide even if it's not.
The Taliban have the abillity to keep us occupied indefinatly by representing a reality that the US and it's allies are simply unable to adapt our morality to. The Nazis were an enemy that we could fight and work to destroy with all our effort, The Taliban so far is not by it's nature.
I know many are going to disagree, but these are my thoughts.