Supernatural: 10 Biggest Unanswered Questions

When demons were first introduced to the show, they were considered to be enemies who were much higher than the Winchesters' pay grade. In the later seasons of Supernatural, demons became almost useless, with Sam and Dean killing them off one by one with ease - only struggling with the odd overly powered demon here and there.

Before the Winchester brothers became buddies with Crowley, their one proper interaction with a demon was the main antagonist (at the time) Azazel, a Prince of Hell. As the show was still new, they had viewers believe demons were extremely powerful beings often only appearing in pivotal episodes in the series. In season 1, Sam and Dean revealed a method of spotting a demon is to speak the word 'Christo', which would then force the demon to reveal his black eyes.

The brothers used this tactic throughout the first season's Phantom Traveller episode and stopped the demon from crashing a commercial plane. However, they never use this method again. If the brothers and other hunters continued to use this method when hunting demons, it would've made their lives a lot easier and their hunts a lot shorter. This seems to be something the writers forgot about or simply thought it wouldn't work when the Winchesters surrounded themselves with demons.