Complex sentence: He was an outcast feared by virtually everyone for his ability to change his face, which in turn made him "cold and cruel" and so he began to abuse others out of resentment for mistreating him and to compensate for his personal crisis.
Split into simpler sentences: He was an outcast feared by virtually everyone for his ability to change his face. This in turn made him "cold and cruel", so he began to abuse others out of retribution and to compensate for his personal crisis.