He suffered an eternity in Hell.
My password is password.

Indeed, he deserved the extended vegetablized treatment instead of Percy, even though that obviously isn't feasible in the scenario.
Rewatching this, I do understand some of the criticisms regarding John's actions of "punishing the bad men". Up to that point he doesn't seem to have a vengeful bone in his body, so it feels a bit out of place when he essentially does a double-kill.
It's also unclear why Wild Bill needed to die at that moment, as he was going to get fried anyway. I used to think that it was mostly Percy himself who did the killing, but I believe it's explained differently in the book as some kind of John avatar with his actions being controlled. It felt a bit like the writer peaking through with "we can't have yet another execution scene so this Wild Bill thread needs to be quickly closed with something more dramatic".

The warden said he killed three people in a holdup. One of them a pregnant woman.

Oh! Right
Well, he was a criminal,so you would expect him to be locked up
If we take the time to see with the heart and not with the mind, we shall see that we are surrounded completely by angels ~ Carlos Santana

But that's not what he's in for, cheeky. John Coffey's in for that, regardless of his not having been guilty.
When you think of garbage, think of Hakeem!
Folks, calm down! This is not the last chopper outta Saigon!

He's the one who raped and murdered those little girls
If we take the time to see with the heart and not with the mind, we shall see that we are surrounded completely by angels ~ Carlos Santana

What was he actually in for? Does it ever say?
When you think of garbage, think of Hakeem!
Folks, calm down! This is not the last chopper outta Saigon!