if am not mistaken, we were told that there are warriors in the empire who are great warrior lvl and above. Thrint's dad is obviously stronger than Venersis by far. I believe the magician and that guy who doesn't talk much are also equal to or stronger than Venersis So I definitely think there are a lot of people who will be stronger than Venersis in the empire Venersis just happens to be the strongest in the desert. We never got shown what the top tiers of the empire look like. If there is no one in the empire who is as strong or stronger than venersis, it will mean there will be no one to challenge Yulian in the empire after he defeats Venersis. Storywise and progression wise that doesn't make much sense.