Sheldon Cooper is at the center of nearly every episode of The Big Bang Theory. As the show's breakout character and de-facto lead, he's the protagonist of most storylines. Most make full use of his character's quirky and obsessive personality to great success, highlighting how much he changes during the show's twelve seasons.
However, some storylines feature Sheldon at his worst. He's morally reproachable, selfish, insensitive, and just plain rude. The show often finds excuses for his behavior and, most of the time, they work. But there are other times where there's no way of justifying his actions, and the audience questions why anyone would ever be his friend.
Paying Stuart To Spend Time With Amy
Sheldon always goes back to his selfish ways. Case in point, the season 9 episode "The Line Substitution Solution." Wanting to get out of spending time with Amy, he pays Stuart to be with her. Instead, he goes to the movies with his friends.
It's not only that he disregards Amy's feelings, but he also takes advantage of Stuart, not that he minds. Sheldon does apologize to Amy in the end, but only because he knows he "has" to and not because he's actually sorry. And Amy accepts his apology, confirming that she's the only one making sacrifices in the relationship.
His Prank On Barry Kripke
Barry Kripke is also quite rude. He often mocks Sheldon, and the two share a troubled yet somewhat respectful relationship. During the season 3 episode, "The Vengeance Formulation," Kripke releases helium in Sheldon's office, humiliating him during a radio interview. Sheldon retaliates by hiding a foam bomb in Kripke's office, which detonates in the presence of several high-ranking Caltech members, including President Siebert.
Sheldon was in his right to seek payback for Barry's cruel joke, but this is one of those times when his supposed superior intellect becomes questionable.
Wanting To Leave Pasadena After Being Robbed
Sheldon notoriously overreacts at the tiniest inconvenience. He dislikes change and often regresses into a childlike state when things don't go his way. In the season 3 episode, "The Bozeman Reaction," he decides to leave Pasadena after someone robs his apartment. After much searching, Sheldon moves to Bozeman, Montana, but quickly returns to California after a local Bozite steals his luggage at the train station.
His friends are all quite shocked that he's actually leaving but aren't that surprised when he eventually returns. Leonard, in particular, just seems tired of his roommate's shenanigans.
"Punishing" Amy For Lying
One of the show's running gags is Amy's desperation for physical contact, which Sheldon refuses to give. Amy often goes to extreme and questionable lengths to get his attention, but things escalate in the season six episode "The Fish Guts Displacement." Amy pretends to be sick, prompting Sheldon to take care of her. She carries on with the ruse even after she gets better, and when Sheldon learns of her deception, he decides a punishment is in order.
The scene that follows is very uncomfortable to watch. Sheldon puts Amy over his knee and spanks her, which she seems to really enjoy. Fortunately, the episode ends before they show more of the weird scenario.
His Behavior After Winning The Nobel
Sheldon, ever the self-centered genius, becomes even more overbearing after winning the Nobel. He's openly rude to his friends, disregards their feelings and problems, and expects them to be at his disposal all the time.
Thanks to some harsh words from Amy, Sheldon understands his accomplishments are not only his own and that he wouldn't be there without all the people in his life who always supported and lifted him. It's an incredible moment of growth for the character, even if it comes after an entire episode of him at his level worst.
Cleaning Penny's Apartment
As the show goes on, Sheldon's love for cleanliness and order becomes apparent. But in season 1, other characters still didn't know just how few boundaries Sheldon had. In the second episode of the series, "The Big Bran Hypothesis," he sneaks into Penny's apartment at night and cleans it.
Not counting the blatant absurdity of the situation, Sheldon's behavior is absolutely reprehensible, and so is Leonard's. By giving into Sheldon's whims, he further empowers him. Penny eventually forgives the guys, but in hindsight, no one would've blamed her if she'd taken a restraining order against the guys.
Demanding Leonard Take Him To Switzerland
"The Large Hadron Collision" is one of the most divisive episodes of The Big Bang Theory. Some argue that Leonard indeed had to take Sheldon to Switzerland because it was part of the infamous Roommate Agreement. Others believe Sheldon acted terribly and didn't deserve Leonard's kindness.
The truth of the matter is Sheldon behaves horribly towards both Leonard and Penny during the episode. He retorts to tantrums and childish antics to get what he wants. Instead, he ruins the trip for everyone involved.
Being Rude To Everyone When He's Sick
Whenever he's sick, Sheldon acts worst than usual. In fact, the first time he gets sick, the guys all avoid him because they know how unbearable he gets. Things reach a new limit in the season six episode "The Empathy Optimization," when he behaves appallingly towards all of his friends, insulting Penny and Bernadette, disregarding Emily's career, and being ungrateful towards Leonard.
Sheldon's entitlement is one of his worst traits, and this is one of the episodes where everyone holds him accountable for his awful ways. In the end, he learns his lesson, and his friends all forgive him.
His Behavior Towards His Assistant, Alex
Season six is a dark time for Sheldon. Numerous episodes feature him at his most rude and insensitive, including all of Alex's appearances. Sheldon hires her to be his assistant and treats her rather badly, although he doesn't seem to do it on purpose at first.
However, when he tries to talk about her "inappropriate" behavior towards Leonard, things get incredibly ugly. He compares her to an "egg salad" and shows her a book full of STDs. The moment is cringeworthy and insulting, and it's a surprise it even aired.
His Behavior Towards Mrs. Davis
In the same episode where Sheldon talks to Alex, he has an equally offensive conversation with the head of HR, played by future Academy Award winner Regina King. Sheldon is openly racist towards her, in a moment that ranks as one of the worst in the entire episode.
In a future meeting, during the episode "The Tenure Turbulence," he gifts her a boxset of Roots, continuing with the racist jokes. These two are arguably the character's worst moments in the show, and fans still wonder why he wasn't fired on the spot.