Originally Posted by sFrog
It's stated that the full power of a beyonder can not be released (without destroying the planet I assume).
Due to that Claude was able to kill him.
The display of powers is somehow funny though. When Claude mentioned Arthur's name Robert was shocked... but when he actually encountered that guy he remained calm and killed him.
Exactly. A Beyonder cannot release it's Primum and use it at the full extent because it would destroy everything. He can use the Secundo without damaging the surroundings though.
Now about Arthur: Robert was shocked because of something. Not because of Arthur, or his powers. But because of what Arthur represented. It will be explained in the next chapters.