Downplayed: Evulz is laughably petty and is ignored because there's a Monster of the Week to take care of.
Although it is acknowledged that killing Evulz would not necessarily be a bad thing, the heroes are a Lawful Good group and firm believers in the principle Thou Shalt Not Kill, preferring to have faith in the courts to mete out appropriate justice.
Evulz does everything in his power to make sure he doesn't stay dead, whether it be cloning, altering his own body or simply using mystical forces to later resurrect himself.
Evulz is immortal. Executing him is not an option, and there's no prison capable of permanently locking him up.
Zig Zagged: This being Joker Immunity, it always is.
Averted: After being captured and escaping twice and just as the trope looks about to take hold, in his third showdown with the heroes Evulz is defeated and killed in a climactic manner, with an appropriate level of emphasis.
Enforced: "We can't kill Evulz! He's far too interesting a villain, if we killed him our ratings would plummet!"
Evulz: "How am I not dead by now?"
Evulz: "It won't matter what you do to me. Arrest me, crucify me, I swear to you I'll be back. Every. Single. Time."
Exploited: Evulz gains enough Medium Awareness to know that he'll just come back from whatever Bob throws at him or throws him at, so he just tries whatever hairbrained scheme he comes up with, knowing he'll live through it.
Defied: After his fourth defeat, Evulz is carted back to his Cardboard Prison and gives Bob a Hannibal Lecture mocking their refusal to kill him and pointing out they'll keep doing this forever, at which point Alice shoots him in the back of the head.
Discussed: "You know, killing him would probably prevent a lot of collateral damage. Sometimes I wonder why we let him live."
Conversed: "You know, it's been years and this guy keeps coming back, after all the stuff that's happened." "I guess the show wouldn't be the same without the bad guy."
Implied: A one-shot story introduces the hero and Evulz, mentioning that they have fought many times. In the end of the story, Evulz is defeated and seemingly killed but the hero firmly believes he'll return, implying that this sort of thing is typical.
Deconstructed: Emperor Evulz constantly causes more and more destruction and death whenever he comes back, to the point that all faith has been lost in the heroes for failing to effectively stop him.