He was always portrayed as an asshole, a thief, a bully, and a prankster. Most of the kids heard the stories and thought he was probably a cool guy to be respected and feared. Eddy emulated him, so you got a taste of what his brother was like all throughout the series.
It wasn't until you got to see him first hand did the audience and the kids understand just how bad he really was. Rolf was probably old enough to see his mischief and mayhem first hand.