Complex sentence: Upon activation, his right arm transforms into a weapon powerful enough to destroy entire cities with a single blast, but does not harm any people in the process, in a manner similar to the effects of a hydrogen or nuclear bomb.
Split into simpler sentences: Upon activation, his right arm transforms into a weapon powerful enough to destroy entire cities with a single blast, but does not harm any people in the process. In a manner similar to the effects of a hydrogen or nuclear bomb.