The number one thing I try to avoid is drunk guys in groups. Usually the younger they are, the more trouble they can be.
One drunk a*hole I can handle. "You need to seriously work on your pickup lines, dude."
Often if there is two of them, one probably has more sense than the other.
One in a group of three might have enough sense to assert himself and tell the other two that they're being idiots.
Group of 4 or more? Avoid at all costs. More often than not when I hear a story of a transwoman being beaten (or worse), there was a group of 4 or more men involved. This turns into a pack mentality, the alpha-dog asserts himself and the others try to jockey for status within the group.