system
Given the following post, respond as if you're commenting on Reddit:
human
[DC] Why doesn't anyone else just kill the Joker?

Why doesn't Lex Luthor just kill the Joker?

Why don't other Batman villains just kill the Joker?

Why doesn't every super-villain in the world just kill the Joker after the shit he pulled in Last Laugh and Salvation Run?

Why doesn't the Gotham Mob just kill the Joker after what he pulled with, say, Carmine Falcone?

Why doesn't the Gotham Police, supposedly most corrupt in America, just kill the Joker? how has he not "resisted arrest" or "Hung himself in his cell" or "Snuck a firearm into prison and engaged the guards in a firefight"


Why doesn't the US government just kill the Joker?

Why doesn't Amanda Waller use the Suicide Squad, sans Harley, to just kill the Joker?

Why doesn't the Spectre just kill the Joker?

 
Why doesn't the Court of Owls just kill the Joker (I'm sure he must have blown up one of their buildings or killed off one of their members at a charity gala or whatever)?

Why doesn't the Green Lantern Corps or the Red Lantern Corps just kill the Joker?

Why doesn't Jason Todd Red Hood and the Outlaws just kill the Joker?

Why doesn't Wonder Woman just kill the Joker, especially after he crippled Barbara Gordon?

Why doesn't Damian Wayne just kill the Joker?

Why doesn't the League of Assassins just kill the Joker?

Why doesn't the state government execute Joker? surely he could be tried for more than enough murders

Why doesn't the staff at Arkham (supposedly an extremely abusive and amoral hospital) kill the Joker? or at the very least permanently cripple him so he'd be easier to handle/wouldn't escape so much

Why doesn't Superman just throw the Joker into the sun?
gpt
The Spectre? 

Thats a good question. Spirit of Vengeance not doing much avenging here. No evidence, but here are some baseless thoughts.

1) Like Dr Fate, the Spectre may work under rules from even more powerful beings. The Joker may be a pet of the Lords of Chaos, or part of some divine plan he is forbidden to interfere with.  

2) The Spectre's current host (if he has one) doesnt care. Maybe old school Jim Corrigan would turn joker into a Joker fish and watch as he suffocates (kinda funny, eh Mr J), but for now the Spectre is playing a long view game.

3) Maybe he has, but someone else brings Joker back or maybe its always a new guy - like a version of Deadman that possesses people. There is no Joker singular, but only Jokers plural. 

4) Maybe the Joker is a vessel, a receiver of mankinds madness, callousness, impulsiveness and dismissal of consequences. Maybe Joker is not like all the other baddies, maybe he is a sin eater. His existence is like a visible sympton of a disease on mankinds soul.