Family Guy Nasty Wolf Pack
The perfect wish to outsmart a genie | Chris & Jack
In all the cases of killing, the robots were innocent. It was either a human that tricked the robot or didn't tell the robot what they were doing.
For example, a lady killed her husband by asking a robot to detach his arm and give it to here. Once she got it, she beat the husband to death and the robot didn't have the capability to stop her (since it gave her it's arm). That caused the robot to effectively self-destruct.
Giskard, I believe, was the only one that killed people. He ultimately ended up self-destructing as a result (the fate of robots that violate the laws).
>A robot may not harm humanity, or, by inaction, allow humanity to come to harm
Therefore a robot could allow some humans to die, if the 0th law took precedence.
IIRC, none of the robots broke the laws of robotics, rather they ostensibly broke the laws but the robots were later investigated to have been following them because of some quirk.