All 3 are "baddies". Most alcohol doesn't contain sugar as what sugar was there to begin with is used up in the fermentation process. Alcohol use can also slow down weight loss as the body will burn alcohol for fuel in preference to fat, so if you can continue to consume alcohol and lose weight on a low carb diet, you're the exception rather than the rule.
If you're going to follow Atkins, sugar, flour and wheat are all off limits. As far as I know, there are no low carb plans that allow pure sugar.