Complex sentence: The series is known for its high levels of bloody violence, including, most notably, its Fatalities--finishing moves, requiring a sequence of buttons to perform, which, in part, led to the creation of the ESRB video game rating system.
Split into simpler sentences: The series is known for its high levels of bloody violence, including, most notably, its Fatalities (finishing moves, requiring a sequence of buttons to perform). The Fatalities, in part, led to the creation of the ESRB video game rating system.