Where do I start? His pop Vito was meant to be feared and all that but he did not come across as cruel but Michael was just cruel, the way he shut the door on Kay's face, lying to a grand jury without blinking, baptising his nephew and at the same time killing all the major players(okay that part1 still!) killing his own brother. The very definition of a sociopath would suit Michael down to the ground, possibly his army background helped to shape his pathology but they guy aint someone you mess with