Generally, people consider Hogwarts' House of Slytherin as the “evil” house — the house that every dark wizard has come from. But they don't deserve this reputation. According to Pottermore, an equal amount of dark wizards come from other houses too, not even Hufflepuff being innocent. Peter Pettigrew was an evil (weak and pathetic, but evil nonetheless) Gryffindor. Professor Quirrell was an evil Ravenclaw. Yet anyone who's read or watched Harry Potter knows that for every evil Slytherin like Lord Voldemort or Dolores Umbridge, there is also a good Slytherin like Severus Snape or Regulus Black.
Hogwarts School of Witchcraft and Wizardry is a questionably competent school with a disturbingly high mortality rate, but even they would account for an entire quarter of the student populace going evil if such a thing happened. So it's probably a non-issue. Perhaps a look at ten characters who would definitely be sorted into the House of Slytherin would support the point that not all of them are fantastical villains in the making.
Plenty of characters from Billions could make their way into Slytherin, but Bobby Axelrod stands out. At the end of the day, if an opportunity for more money and power rises, or if the affiliated party in question has slighted him in any way, real or imagined, said party can expect an axe in the head (Get it?).
Billions is all about staying a step ahead in the world of big money. And in the name of this, Bobby Axelrod refuses to lie to himself or hold onto someone he deems a loser.
Ambitious, determined, and unfettered, Scarlett O'Hara would fit right into Slytherin. Would a Gryffindor even conceive of marrying their sister's beau to take over a lumber mill and save her beloved home? That sort of serious determination and willingness to do whatever it takes to save herself and the land she (begrudgingly) loves is all Slytherin. It's really unfortunate that she thinks she's in love with such a placid Hufflepuff for so many years. Yet, by accepting who she is, she ends up with Rhett in the ultimate Slytherin power couple.
Tyrion, Jaime, Cersei. All Lions of Lannister, all worthy candidates for the snake house at Hogwarts. They love power and bare a worldly perspective that allows them to leverage wealth to become the house in Westeros that always pays their debts.
Cersei demonstrates the selfishness of a traditional Slytherin in the Harry Potter universe. She's a complex but undeniable villain with all the lies, manipulation, and subterfuge that a dark wizard would root for. However, as Slytherin is one of the more interesting houses, Cersei is also one of the more enjoyable characters in the show. Jaime, on the other hand (er, position), shows the complexity and potential for change a Slytherin might have.
And though Tyrion betrayed his family after their abuse, he still stands as a Lannister and a Slytherin. He carved himself a reputation for being crafty, logical, and realistic in the face of the cold world he lives in. Throughout his tenure as Hand of the Queen, he attempts to rein in Daenerys' hot-blooded traits with more worldly plans. And given the results of said hot-blooded traits getting the better of her when it mattered the most, Tyrion shows the value of having a Slytherin around.
While not all Slytherins are evil, no other house would indict a member willing to destroy a five-year-old girl's life to keep his boyfriend from leaving him. Lestat is a snob and a little bratty but also ends up becoming the most powerful vampire in the world. A French aristocrat such as Lestat de Lioncourt, with a desire for the finer things in life and gothic sensibilities, would be right at home in the dark Slytherin common room. Lestat's bratty personality, lust for power, and penchant for drama would likely even make him a Slytherin prefect.
He IS Iron Man. This genius billionaire playboy philanthropist would make for a quintessential Slytherin. His ambition, genius-level intellect, moral complexity, and textbook narcissism wouldn't be out of place in the typical Slytherin seen in the books and movies. However, while these traits would usually create a villain, in Tony and Robert Downey Jr.'s performance, they make him a fascinating character adored worldwide by fans. He won't immediately lay down on a wire and make the sacrifice play, but he'd be the one guy practical enough to just cut the wire.
Here's a classic Slytherin. Doctor Strange is a hard worker, cold, precise, and more than a little full of himself. He starts the MCU as a self-centered glory hound who avoided doing anything too difficult for fear of staining his perfect record. And then he became a selfless champion willing to die to Dormammu in perpetuity and obscurity to spare Earth and the rest of the multiverse from his evil. Much like fellow Slytherin Severus Snape, he is a heavily flawed man who is willing to sacrifice everything to do the right thing. The Sorting Hat would definitely know where to put this good doctor.
Much like the Malfoy family, Clay from Sons of Anarchy would stab anyone in the back to advance himself or save his own skin. He demonstrated this when he killed the two founding members of SAMCRO. However, a better Slytherin would have had enough foresight to see the inevitable consequences of this betrayal.
He sealed his own fate even before the unanimous SAMCRO vote to kill him. While he shows treachery and tactical skills fitting of a Slytherin, he shows lower rung strategic chops.
Peeta might look like a Hufflepuff, but nope. It was Peeta's idea to fabricate a romance with Katniss to cause civil unrest around the Hunger Games. He also knew how to work a crowd where Katniss could barely even stomach being on television. During the games, he manipulated the career tributes, joining them safely despite not taking a single life in the book or the movie. When that plan eventually backfired, he literally blended in with the forest to hide from the other contestants. Peeta survived the Hunger Games and made history by doing it alongside a second contender. And he did this by being a Slytherin champ. Slytherin wins the Hunger Games!
BBC's favorite high-functioning sociopath might be a Ravenclaw. Even the Sorting Hat might have a hard time deciding where to put him. He's phenomenally intelligent and strategic like most Ravenclaws. He even has an eccentricity to his brilliant way of thinking like Luna Lovegood. However, he also has an arrogant and distant disposition that tends to alienate the people around him. Additionally, he utilizes his intelligence in a highly specialized way rather than a more comprehensive one; he knows the soil composition of nearly every English county but doesn't know that the Earth revolves around the sun. If Sherlock were in the Slytherin dungeons working on curses and potions, he would be right at home. While his obsessive personality and love of showboating his intelligence might annoy the other Slytherins, he would still belong there.
The Count of Monte Cristo himself would make for a textbook Slytherin. Where else would the Sorting Hat place someone so dogged and meticulous in his quest for revenge? For a while, he held onto his hate with the belief it was all he had left. And the people who ripped his world away from him had their own ripped from them with brutal precision. However, in whatever incarnation he appears in, watching his scheme unfold is incredibly satisfying - all because his victims deserve their punishment. And as any Slytherin would tell you, revenge is a dish best served cold.