The Biggest Mistake Sam Ever Made On Supernatural
"Supernatural" is one of the longest-running and arguably most successful shows on The CW network — so long-running, in fact, that fans who started watching the series on day one can remember that the channel used to be called The WB. The series revolves around the Winchester brothers, two specially trained "hunters" who eliminate malevolent beings (demons, Wendigos, vampires, and more) from the face of the earth. But the boys are human, and humans make mistakes. This statement is especially true for Sam and Dean Winchester, played by Jared Padalecki and Jensen Ackles, respectively.
In a recent Reddit thread, u/laurendonofrio asked fellow fans for their opinions about which character in the show makes the worst mistake of the entire series. Now, every true "Supernatural" fan knows that the correct answer to that question is "everyone, for not eating enough pie." But despite that irrefutable logic, lots of the opinions shared in this thread happen to revolve around Sam and some of his less-than-optimal choices over the years. There is a noticeable pattern, though, and that pattern reflects a very disastrous choice Sam makes early on in "Supernatural" Season 4 which has some long-term repercussions.
He trusted a demon and almost ended the world
Both u/s8n_isacoolguy and u/kh-38 mention in the Reddit thread how one of the biggest mistakes Sam ever makes is trusting Ruby the demon (Katie Cassidy/Genevieve Padalecki), the malevolent seductress who gets him high on her blood and gives him supernatural powers. But the only reason she ever helps Sam is so that she can use him in order to break open the 66 Seals which are preventing Lucifer (Mark Pellegrino) from escaping Hell. Ruby believes that Lucifer will reward her (and Sam) for her efforts, but she then gets killed shortly after completing her task by Dean, with some assistance from a confused and betrayed Sam.
This MsMojo video on YouTube discusses the same thing in more detail, breaking the blunder up into two different segments. Even Screen Rant agrees that it is such a big mistake that it deserves to be broken down into parts. But all of these events are just consequences that extend from the same, simple origin point: a hunter, born, bred, and destined to eliminate evil demons from the earth, betrays everything and everyone he knows just to make his job a little bit easier.
Does Sam really need Ruby's demon blood powers to do what he does in the name of good? Arguably, no. He could do it all without her help and avoid starting an apocalypse. But instead, Sam gives in to temptation, which sends "Supernatural" down a spiral that takes an additional 11 seasons to resolve.