At one point in the storyline, our protagonist and his posse have broken into the enemy hideout to save their captured friend. Naturally, our protagonist pulls out his giant sword and offers to hold off the entire room full of vampire enemies so that everyone else can continue the rescue mission. As vampire Henchman #1 steps forward, our protagonist makes a snide comment about it being 7 to 1 odds. To show just how pathetic he thinks our hero is and how little he's concerned about him, Henchman #1 calls out to Head Vampire and asks him to put down the trinket that's the source of all his power and will leave him defenseless. Head Vampire complies and walks away from the item. Henchman #1 says this shows the battle will be even because if any other vampire henchmen jump in, our hero could just attack and destroy the Head Vampire who is now defenseless. Cue the start of battle.
I can't be the only one who immediately thought the first action should be to cut Head Vampire in half, can I? Honor and good form are nice and spiffy but dead men tell no tales. You could also argue the villains were stupid for going along but maybe Henchman #1 thought it was a good opportunity to move up in the hierarchy and chances are Head Vampire had a backup plan anyway. Still, you never know until you try.
I find that I'm incredibly practical about things like this which is probably why it's a good thing I've never been chief strategist for any major war. I'd be ordering firebombings and mass poisonings if I thought the situation called for it. If the ends are big enough, you can push through almost any means.
So it turns out Henchman #1 did have betrayal on the mind and the Head Vampire DID have a backup plan. Looks like the only one who was stupid was the Hero.