I love how people underestimate Slytherins’ loyalty. It’s not always the loyalty you think you would see, they do everything the way they want to and they are loyal to the people who they want to be loyal to. You cannot make a Slytherin do something they don’t want to if they are not loyal to you.
Narcissa Black: literally looked Voldy in the eyes AND LIED, like the nerve it takes. She looked Death in the eye and lied for her son.
Regulus Black, I’m not even explaining this. The kid died out of his loyalty to Kreacher??
Severus Snape: his loyalty to Dumbledore (not to anybody else but to him). This may not be a popular idea but good lord that man did some crazy stuff out of his loyalty to Dumbledore.
Bellatrix Lestrange: went to prison, came out never changed her ways. She was loyal to Dark Lord to the end. Borderline obsessive but at the beginning everything she does is out of loyalty.
Andromeda Tonks: her loyalty to her family knows no bounds. Not to her blood family but to her real family.
Draco Malfoy: who almost killed his headmaster because he wanted to protect his family and himself.
I’m sure there are more examples but these are the ones that came to my mind. Do not underestimate Slytherins my dears.