Complex sentence: Tōma Kamijō is a student in Academy City whose right hand, the Imagine Breaker, has the ability to negate any supernatural power, but also negates his own luck, much to his chagrin.
Split into simpler sentences: Tōma Kamijō is a student in Academy City whose right hand, the Imagine Breaker, has the ability to negate any supernatural power. But his ability also negates his own luck, much to his chagrin.