He turns on Voldemort and works for the other side because Voldemort went after Lily. In short, Snape favors Draco because Lucius was his old friend and Snape has a rather difficult time separating children from their parents.
He is his godson and the child of his good friend Narcissa and fellow former death eater Lucius. He is fond of Draco if you could call it that. He doesn't like Harry at all.
Although Snape may not have projected his memory of James onto Harry, he still would have been predisposed to dislike him by virtue of him being James Potter's son. Harry being in Slytherin would not have changed this fact.
Because the Malfoys were a family who held Severus with appropriate deference and respect.
Specifically, Draco was jealous of Harry. It was easy to miss because Draco didn't often show his emotions, modelling himself on his cold, confident, calculating father, but J.K. Rowling has confirmed that a lot of his enmity towards Harry stemmed from envy.
“Harry was constantly crushing on Draco. He just couldn't hide it.” In the books and movies, Harry and Draco are constantly at each other's throats, given that Draco's parents are Voldemort supporters and the evil wizard killed Harry's parents.
Draco had several reasons for lying to Bellatrix, including the fact that he was never a bad person. Moreover, he no longer found working for the Dark Lord appealing and hated how Voldemort treated his family. He did not intend to harm anyone and believed Harry was the only person capable of defeating Voldemort.
Most probably not. Snape's hatred of Harry came from having to see James's face every day and Lily's eyes behind his glasses. Harry would've been a constant reminder of the love Snape lost, and I believe it would've been more painful if he was in Slytherin because they'd have to see each other more.
He doesn't trust Snape as Dumbledore does, but he believes that he can detect any disloyalty. Moreover, Voldemort regards Snape as highly intelligent and therefore ' as a true Slytherin ' a person whose top priority is to take care of himself. To his twisted mind, selfless equals stupid.
There are two reasons why Snape agreed to protect Draco. He was somewhat forced into it. Narcissa asked this of him, and refusing would have looked weird; since he was supposed to be a follower of Voldemort, it wouldn't have been a big deal to protect Draco and 'help' him in his task to kill Dumbledore.
Snape Wouldn't Hate Her So Much
Harry reminded Snape of James, but if Harry had been a girl, he may have reminded Snape of Lily instead. Meaning Snape would have been a lot more eager to protect and help girl Harry throughout the series.
Later in the year, Dumbledore revealed that Harry was in fact a Horcrux, meaning that he would eventually have to die. Now, as firmly established, Snape was not the greatest fan of Harry, but that didn't mean that he ever stopped loving Lily. Dumbledore was surprised that Snape seemed to care for the boy.
A Professor at Hogwarts School of Witchcraft and Wizardry, Snape is hostile to Harry due to his resemblance to his father James Potter, who bullied Snape during their time together at Hogwarts. As the series progresses, Snape's character becomes more layered and enigmatic.
Harry, however, had never been less interested in Quidditch; he was rapidly becoming obsessed with Draco Malfoy.
Another possibility is that Snape is aware of the origin of the hex Harry cast upon Draco. Snape's immediate demand to see Harry's Potions book suggests strongly that Snape knows where the Sectumsempra spell originated, and also perhaps that he is its original author.
Bellatrix Lestrange (née Black) is the first female Death Eater introduced in the books. Aunt of Draco Malfoy and Nymphadora Tonks. She was introduced in Harry Potter and the Order of the Phoenix. She is the most faithful member of Voldemort's inner circle.
In order to preserve his position as a trusted Death Eater, Severus Snape was forced to tell Voldemort the true date at which the Order planned to move Harry.
For the Potter uninitiated, “always” is how Snape explains to Dumbledore in the final book why his Patronus takes the same shape as the one belonging to his long-lost love: Harry Potter's mother, Lily.
Worst: Lucius Malfoy
Lucius Malfoy is pretty clearly a bad person, but he's a perfect example of how banal cruelty and evilness can be. Lucius likes to control, humiliate, and cause people pain, but he's also too weak and self-absorbed to really become one of the evil "greats," so to speak.
Horace Slughorn (1997 - present) Horace, after being convinced by Dumbledore and Harry Potter, returned to Hogwarts as the Potions master. After Severus killed Dumbledore and became headmaster of Hogwarts, it was decided that Horace was to become the Head of Slytherin House once again.
Harry revealed that Draco was still very much alive, and she lied to her master in order to get closer to him. Narcissa may have concealed the truth from Voldemort to save her son, but she inadvertently helped Harry to victory in doing so.
Draco Malfoy's mother Narcissa was cold, cunning and devoted to the Dark Lord. But she was also a mother, which meant she was willing to risk everything to make sure her son was safe. When Harry survived Voldemort's Killing Curse for the second time, Narcissa pretended he was dead so she could get to Draco.
Bellatrix Lestrange Killed her own cousin, Sirius Black: She killed Sirius (who was her cousin) during the battle at the Department of Mysteries. She was remorseless and was cackling in glee after she had murdered Sirius.