The Hogwarts House of Slytherin was given an especially bad rap in the Harry Potter series. However, since then, additions to the lore have shown more positive sides to the House, and proud real-life Slytherins have come to the defense of their House.
Nevertheless, although fans now have plenty of great Slytherins to look up to, it can never be denied that Salazar Slytherin's House has produced some of the most evil witches and wizards in the history of the Harry Potter universe. While there are doubtless many more evil Slytherins, this list will only cover characters who are confirmed to have been sorted into Slytherin.
7 The Bloody Baron
The Bloody Baron, the man who would go on to become the ghost of Slytherin, was one of the very first students to be enrolled in Salazar Slytherin's new House. He is also the man who killed the daughter of Rowena Ravenclaw after tracking her down in Albania and having his advances of love rebuffed yet again.
While he instantly regretted what he'd done and took his own life in remorse, to kill someone in such a fit of rage is still an act of evil, and the Grey Lady tells Harry that he was always a hot-tempered man. If he was capable of this, then it is likely he committed other cruel acts during his lifetime.
6 Lucius Malfoy
Just because Lucius Malfoy failed to achieve practically anything, it does not mean that he is not evil, seeing as his intentions certainly were. Easily the worst thing that Lucius Malfoy ever did was plant Tom Riddle's old diary among Ginny Weasley's possessions.
Even though Lucius did not know exactly how it would work, he did know that he was helping to open up the Chamber of Secrets, which could result in the deaths of children. In the film version of The Chamber of Secrets, Lucius Malfoy even attempts to kill Harry with Avada Kedavra, for freeing his house-elf.
5 Amycus & Alecto Carrow
The wizarding school year of 1997-1998 was easily one of the worst times to be a Hogwarts student. In large part, this was thanks to Amycus and Alecto Carrow, two Death Eaters who were appointed as Hogwarts professors.
The pair were extremely cruel, not only teaching an entire generation of children the wrong sort of life lessons, but shockingly also torturing them. Students could be chained up and slashed or beaten. Amycus Carrow in his role as Dark Arts teacher went as far as to have his seventh years practice the Cruciatus Curse on students in detention.
4 Salazar Slytherin
Salazar Slytherin, the founder and namesake of Slytherin House, is a highly divisive figure. For most of his life he was a highly respectable founder of Hogwarts and one of the greatest wizards of his time.
However, the fact that he left behind a Basilisk in a school to be used to murder Muggle-born students, instantly puts him high on the list of most evil Slytherins. The sick use of Unforgivable Curses as security for his scriptorium in Hogwarts Legacy is also highly disturbing.
3 Dolores Umbridge
Despite her pink and frilly attire, there are things about Dolores Umbridge that in some ways make her worse than Voldemort himself. For example, in her short tenure at Hogwarts, she used an abhorrent form of punishment on the students, literally making them bleed. To make this worse, it appears that she even found joy in this.
While Umbridge did plenty of awful things at Hogwarts, it didn't stop there after her return to the Ministry of Magic. Under the rule of Lord Voldemort, Dolores Umbridge had Muggle-borns tortured and sent to Azkaban, solely for their lack of magical parents.
2 Bellatrix Lestrange
Bellatrix Lestrange is pretty much the definition of evil, and the worst part about it is that she appears to have no other motive than enjoying the sensation of inflicting pain in others. One of the worst things Bellatrix ever did was to destroy the minds of Frank and Alice Longbottom by using the Cruciatus Curse to try and get them to reveal the location of Lord Voldemort after his downfall.
She took glee in seeing their son Neville try and stand up to her, and also boasted and laughed about killing her own cousin Sirius Black. Bellatrix doubtless committed many more acts of evil all for fun.
1 Tom Riddle / Lord Voldemort
When it comes to the most evil Slytherins, there is only one in contention for the top spot. Tom Riddle who would go down in the history books as Lord Voldemort. Blinded by his lust for power and immortality, Lord Voldemort was willing to commit any crime, murdering countless individuals over the years.
From murdering his father and grandparents to unleashing the Basilisk on Hogwarts' muggle-born students, Voldemort placed no value on life apart from his own. His two reigns of terror saw other atrocities committed either at his behest, or because they were permitted. The amount of suffering that Voldemort brought into the world easily makes him the most evil Slytherin.