I hope so. Remember that Severums are cichlids just like Oscars. Just because I've got two Severums that are very placid and a joy to have, there are bound to be people who have Severums that aren't so nice.
The best way to avoid aggression is not to overstock an aquarium. As soon as you start cramming fish in together, fish are going to start getting knarked with each other and that's when fights can start breaking out.
In the wild, they will avoid each other. Having said that, I was watching a fascinating program the other day about the Amazon and right in front of the camera,an Arapaima swallowed a fully grown Oscar. Quite a sight. But then again, it's not surprising as these are one of the biggest freshwater fish in the world.