Small things can likely be forgiven, but large issues might just make a Slytherin come to lose trust. Another Slytherin trait is self-preservation, may mean choosing not to forgive someone who they believe may wrong them again.
Slytherin House is linked to the element of water, which is associated with imagination, intuition, nurturing, coldness, and emotion. Slytherins are highly emotional, though they chose to think with their heads.
Slytherins can most certainly be caring and kind and empathetic. That said it makes sense why most bad guys would be in Slytherin, since more ambitious and cunning ways of being can lead to big headedness and manipulation.
slytherin: slytherins like to keep their anger under control, so they don't often let it show. when they do, they tend to get angry over people insulting things that matter to them, and people questioning their knowledge on something they know a lot about.
After a fellow Slytherin, the next best match for this shrewd house would probably be Ravenclaw. A Slytherin could use Ravenclaw's intellectual and inquisitive nature to their advantage, plan their world domination in minute detail.
Slytherins are often self-assured and confident of their own competence, but we like to think that this also means that they can be confident on your behalf. They're good at recognising when someone excels, and will push you to keep excelling.
Slytherins are hardworking and desire success. They are known to achieve great things (even if not always good things). They are the kind of people who make you want to be better just by being around them. They are determined and resourceful.
And that's pretty unfair for the majority of people who actually get sorted into Slytherin when they're innocent, wide-eyed 11-year olds. Take these three Slytherins: Malfoy, Snape and Slughorn. Three wizards not without their flaws.
The most famous Slytherin in Harry Potter is Salazar Slytherin, one of the four founders of Hogwarts. He was also known as one of the most brilliant wizards of his generation. Salazar was skilled in Parseltongue and crafted his personal wand out of snakewood and a basilisk horn.
They may not have been fighting by his side, but they were still fighting ON his side. So it would appear that each and every Slytherin student fought for Voldemort bar none, and the only Slytherins who fought against Voldemort were the teachers - Slughorn, openly, and Snape, covertly.
They don't give up. This ambition and drive makes Slytherins pretty single-minded in their pursuits – from Horace Slughorn trying to make friends with the great and good of the wizarding world to Voldemort trying to take it over, they definitely do not give up easily.
There might be discord in the relationship, but Slytherins and Hufflepuffs bring out the best in each other more often than not. Though Slytherins tend to be shrewd, they don't direct this Machiavellian behavior at their Hufflepuff companions and see themselves as one-half of an equal partnership above all else.
“Hufflepuffs are known to have good friends in Slytherin. Hufflepuffs are some of the few who won't judge based on negative rumours. This means they're the most likely to approach Slytherins and help them when in need. This makes amazingly loyal friends between the houses.