Sabrina's death
Is really Elizabeth's fault. Seriously think about it.
If Liz weren't so hellbent on sending Hayden to prison she wouldn't have been rushing to get to the police station. Then she would have waited for the elevator and would not have been pushed down the stairs. If Liz weren't in the hospital Sabrina would not have been in her room and offered to care for her since the hospital was short staffed. Then Monica would not have been reminded of how good of a nurse Sabrina is and offered her a job at GH. Then Sabrina would not have seen Paul at the hospital and he would not have had to kill her to keep his secret safe.
Honestly I think almost every bad thing that happens in PC can be traced back to Liz.
The greatest trick the devil ever pulled was convincing the world he didn't exist