The criminal/villain organization tries too avoid hiring people who are too evil because the leader feels that Even Evil Has Standards and that anyone who was more then willing to cross the line was more likely to be okay with the idea of betraying them.
It turns out that the gun didn't have any bullets in it, and the character realized that.
Or, it turns out this was a Secret Test of Character and anyone who actually goes through with it is too mentally unstable to be reliable...
It turns out that the gun was loaded with blanks; but the second step is to hand the participant a live gun, just to see how the participant reacts to their mind being screwed with.
Zig Zagged: Bob is asked to prove his villainy, by petting a kitten. When he agrees he has a metal glove handed to him... only, it's just a grooming glove, and the cat enjoys it. But dies seconds later, because the glove is poisoned! The Big Evil comments "Since when do we poison grooming gloves?"
Averted: The character gets in without any tests of loyalty.
Enforced: Show writers think that the audience really need an highlight on who is the bad.
Lampshaded: "I'm a veteran, I served under dozens of Evil Lords. Luckily, I like the taste of kittens."
"What, you think I'm going to get my own hand dirty? I'm a schemer, I don't kill directly."
The hero secretly frees every kitten in the Evil Lord mansion before being tested.
Discussed: "I expect you're suspicious of my sudden change of heart, aren't you? Gonna ask me to prove my evil?"
Conversed: "What is it about villains that they feel like they have to demonstrate their evilness in such an over-the-top way?"
Deconstructed: "You know, forcing all recruits to go through such a dehumanising act, to say nothing of the inherent lack of trust in your hiring practices this implies, may go a long way to explain why the crime syndicate over in the next city has three times your members since all they want is a simple referral. I mean, what does this even prove? If anything, if I go through with this should make you even more worried about my loyalties since it either proves I'm a complete sociopath nutcase, or someone who's ruthless enough to do such a thing just to keep my cover. I mean, imagine if I'm an undercover Action Hero: What do you think I'm going to do to you later for putting me through this?"
Reconstructed: "You want to join us? Kill one of us, and take his place." "SURE!" *BANG!*