Unpopular opinion: morally, I think Deb is worse than Keith, and Keith is worse than Dan
I know Dan actually killed Keith, so on the surface this probably sounds insane. But I’m ranking them based on morality, intent, and how justified each person reasonably believed they were, not simply who caused the worst outcome.
Deb is the worst.
Deb actually went through with an attempt to kill Dan. She drugged him and set the dealership on fire while he was inside. Dan was unarmed, wasn’t trying to kill her, and as far as we know had never even considered murdering her. Whatever horrible things Dan had done to her, this was still a deliberate murder attempt without Dan having first tried to kill her.
Keith is second.
Keith got drunk, bought a gun, and genuinely decided he was going to kill Dan. At that point, Dan had never tried to murder Keith either. The reason I put Keith below Deb is simple: Keith ultimately changed his mind and backed out. That matters morally. But he still got frighteningly close to committing an unjustified murder.
Dan is actually third for me.
What Dan did was obviously wrong. Keith was unarmed, Dan didn’t have absolute proof, and he executed him rather than going to the police.
But Dan also had something Deb and Keith didn’t: a very strong reason to believe his target had already tried to murder him.
Dan knew somebody had drugged him and left him to die in the dealership fire. The evidence pointed toward Keith, and Keith had plenty of reasons to hate Dan. We as viewers know Deb actually started the fire, but Dan didn’t know that.
And the craziest part is that Dan was wrong about Keith starting the fire, but he wasn’t completely wrong about Keith wanting him dead. Keith really had decided to kill Dan that same night before backing out.
So morally my ranking is:
Deb > Keith > Dan
Deb tried to murder someone who hadn’t tried to murder her. Keith planned to do the same thing but thankfully stopped himself. Dan actually committed the murder, which is the worst outcome, but he did it while genuinely and reasonably believing Keith had already attempted to kill him.
Dan was still wrong. I just think his actions were more morally understandable than either Deb’s or Keith’s.