The difference is clear: ultras do not fight, they create the atmosphere inside and outside the stadium. Being casual has purely to do with wearing a certain style of clothing. And a hooligan likes to use violence for his club.    An ultra can dress casually, but not necessarily like to use violence. And a hooligan may like to use violence, but does not necessarily have to wear expensive brand-name clothing; so does not necessarily have to have anything to do with casual culture.