What I’ll be talking here is the true personality of someone who was sorted in the house of Salzar Slytherin. I think that what makes a ‘Slytherin’ a ‘Slytherin’ is so much more than a few general abilities or beliefs. What makes a ‘Slytherin a Slytherin’ is the inner core of their personality. Here I’ll mention some traits that I believe all Slytherins share without difference.
They hate being vulnerable and weak more than anything: You may say that we all hate being in situations where we are weak or vulnerable, but what we are talking here is the degree. Slytherins hate being weak or vulnerable more than anything. It was this hatred that made Snape call Lily a Mudblood. He was being humiliated by James Potter ,and when Lily came to rescue him, he was so embarrassed that he was being humiliated by the Marauders that in attempt to make himself look stronger and bigger he called Lily a Mudblood, a thing which he regretted his entire life.
They need to feel special: As we know it, all of the death eaters including Voldemort are from Slytherin. What they have in common is obvious; they are racists and pure blood supremacist. One of the qualities that all Slytherins share is that they need to accomplish something great in their lives or be someone great in their lives. If Harry was truly a Slytherin, he probably would have chosen Slytherin when the sorting hat told me that being in Slytherin would have made him great or lead him toward greatness. Beside everything, we know that the reason why someone may be racist is because they want to feel special so much that they make themselves believe that their race/nationality/country/whatever is superior.
They overestimate their abilities: I think that Slytherins, in general of course, are clever and determined, and able to achieve brilliant things in their lifetime, but what they have in common is that they overestimate their abilities. If anyone from your group of friends or family, tries to achieve what others might find impossible, than he/she is probably a Slytherin, and after all wasn’t Voldemort trying to achieve true immortality, something that even the bests of wizards or witches wouldn’t even dream of achieving. Gryffindors have their ambitions, but Slytherins’ ambitions are a whole new degree. You may even call them stratospheric.
They hate rules: What Dumbledore said to Harry ,when Harry was worried whether he didn’t belong in Gryffindor, is that Slytherin have ‘a certain disregard for the rules’, and I find that completely true. But, this isn’t just a hatred for rules. I think that Slytherins hate being told what to do, especially when it’s not in their favor. Even Slytherin hatstalls like Pettigrew, who had cheated on his OWLs, or Harry (Sorry for mentioning them in the same sentence!), who didn’t mind wandering in the corridors at nighttime, do not like rules and sometimes they disobey them.
They have a great ability of understanding others’ minds: I think that Slytherin observes others more than the rest of Hogwarts. As we know it, when it comes to pretending to be someone else, Slytherins are the best. Wasn’t after all, Barty Crouch Junior, who despite knowing so little about Mad-Eye was able to portray him perfectly, deceiving even Dumbledore?
They have many repressed feelings: From what I’ve learned while reading “Harry Potter” is that in order to be good at Occulmency you must be good in suppressing certain feelings and thoughts. That’s why Draco is so good in Occulmency. He is not a decent person, but he is not a bad person like he father was. Once, he was asked to commit murder, he was surprised to find in himself such disgust towards murder. He fooled himself into thinking that he was exactly like father.
They are capable of feeling great love: Weren’t Andromeda Black and the Voldemort’s mother Merope Gaunt, the ones who abandoned their families for love? Slytherins, regardless their reputation, are capable of feeling strong love and passion toward their loved ones.No matter how much time had passed, Snape always loved Lily, and after all this time his love for her never diminished.
Other traits: Slytherins can be quite distrustful of others ; Slytherins don’t like trouble; Slytherins are truly afraid of being humiliated;Slytherin will get angry if they are ignored.