Stefan Salvatore is arguably the main protagonist of the entire The Vampire Diaries series. Admittedly the show did focus on Elena Gilbert for the first six seasons, but Stefan was in the show right up to the very end. Fans saw him at his best and most selfless, and also at his worst, without a shred of humanity.
During his many years of vampirism, it's fair to assume that viewers still don't know everything about Stefan's life. However, despite his attempts to be good and kind, Stefan has still made some pretty major mistakes.
Jumping Into A Vervain-Filled Well
The popular adage 'look before you leap' has never been so apt. During the show's second season, one of the main themes throughout was the search for the elusive moonstone and the mystery of what it did.
Having managed to secure a lead on the stone's whereabouts, Stefan found it at the bottom of a well. Desperate to retrieve it, Stefan jumped right in but discovered the well's waters had been laced with vervain, burning Stefan with every move he made.
Falling In Love With Katherine
Throughout the duration of Season 1, Katherine Pierce appeared predominantly in the form of flashbacks, as everyone thought she was dead in the present. It transpired that she was the one who turned the Salavatore brothers into vampires.
However, before she sired them, she seduced Stefan and Damon, causing them to fall in love with her. For both of the brothers, loving Katherine was one of their biggest mistakes in life, as she was a cold, calculating and selfish woman who brought misery to many.
Switching Off His Humanity
Considering that The Vampire Diaries only ran for eight seasons, Stefan really liked to turn off his humanity, having done so no fewer than three times in the present day alone. Admittedly, he was forced to every single time, but it sure made for entertaining viewing.
However, although apparently having no emotions is quite freeing from a certain perspective, it comes with many drawbacks. The main one is, when you finally turn your humanity back on, you regret everything you did when you were a soulless monster, and Stefan did love a good pity party.
Killing Enzo
In The Vampire Diaries's eighth and final season, things got pretty bleak for the Salvatore brothers and their allies. Not only were they up against the Devil himself, but Damon and Enzo were enslaved by the Sirens.
Fortunately, Enzo and Damon managed to break free, but at the cost of Stefan's humanity. This turned him into a monster who hunted down Bonnie Bennett and Enzo, in search of the cure. Stefan found the cure, but not before he ripped out Enzo's heart in front of his beloved Bonnie.
Rejecting Caroline
There were hints of Stefan and Caroline Forbes's budding romance way back in the Season 4 finale, but before they officially became an item, they were the best of friends. They supported each other in a way that seldom other characters had before them.
It was only a matter of time, then, they they developed feelings for each other. Caroline began to fancy Stefan in Season 6, and she revealed how she felt to Stefan at her mother's funeral. However, Stefan rejected those feelings, leading Caroline to turn off her humanity.
Fighting With Damon Over Elena
In all fairness, Stefan did love Elena first, and she him, but he wasn't exactly graceful about the whole situation when Elena dumped him and started dating Damon. Elena and Stefan had been in a relationship for 3 years before calling it quits in Season 4.
What makes this mistake particularly stupid is that the events had already been played out years before, with Katherine. Elena was great and likeable but no one should come between two brothers, especially those who have been through so much already.
Forcing Damon To Become A Vampire
When Damon and Stefan first met Katherine, they were both human, and young, attractive men. It's hardly Katherine's fault that she seduced them both to suit her own needs. In fairness to her, she did genuinely love them both at the time.
In fact, she used her blood to turn them into vampires. Stefan turned first but Damon refused to drink human blood, not wishing to live without Katherine. However, Stefan didn't want to be alone, so he practically forced Damon to drink human blood and complete the transition.
Returning To Mystic Falls
The town of Mystic Falls was home to Elena, Caroline, Bonnie and all their other supernatural friends they met during the show's original run. It was also home to Damon and Stefan, but prior to the first season, they had been away for quite a long time.
Stefan returned to Mystic Falls shortly before the series premiere. It's not wholly unfair to state that a lot of the events that befell the town wouldn't have happened if Damon and Stefan hadn't moved back into town, thus endangering all the local residents.
Trying To Kill Klaus
Stefan's entire schtick throughout the show's run is that he is the 'good brother', according to Damon. He feeds off of animals because he doesn't want to hurt or kill any humans, and he's almost always against inflicting pain on others, no matter how necessary it may be.
However, there have been moments throughout the series where Stefan has slipped up. For example, in Season 3, he really wanted to kill Klaus Mikaelson, despite this meaning that all the vampires that Klaus had sired would also die.
Trusting Katherine
Katherine Pierce was The Vampire Diaries's main antagonist for its entire run. She made for a great villain because of her personal connection to the Salvatore brothers, and for being Elena's doppelgänger. In the end, she was despised by everyone in the main cast.
Despite hating her on occasion, Stefan was the one person who showed Katherine an ounce of compassion every once in a while. Underneath it all, he probably did love her slightly, but every time, she would show him just how wrong it was for him to trust her.