What if an almighty God created the universe without evil, but with free-will, and then one angel decided to challange the way God rules, so that God has to let him rules to show everyone whose way of rule is the best?
Simply killing that angel would not answer the challenge, on the contrary, killing that angel would demonstrate that God is a dictator.
God is already a dictator by choosing the state of everything. Designing a chaotic system and letting it run also supports being a dictator. He designed the system. An omnipotent God is unable to escape His own designs. The rebellious angel was by design. His planning thereby is guile.
Prove there is free will anyways. All modern studies of the brain and consciousness indicate our free will only exists in a compatibalist way, in other words we can be free to act without another actor forcing us. But libertarian free will, such as would be required for any being to act against their "design" has no evidence whatsoever.
Still wouldn't answer why god doesn't interfer with evil. Why doesn't he help us against this angel? Heals sicknesses? Stops wars? Saves victims of murder and rape?