Good point, being under threat is a third knob. Still very simple.
> or any of the dozens of other shades (car accidents?)?
Again, car "accidents" are always due to negligence somewhere, either mechanical failures making the manufacturer liable, or distraction on the part of a driver, or inebriation, etc. These are all very simple considerations that everyone understands.
> So two people getting in a fight in a bar and one unintentionally kills the other should receive the same sentence as car accident victim?
Killing someone in a bar fight is third degree murder, so I've already covered that. If your "car accident victim" had intent to cause harm with his vehicle, that's murder too.