The initial trauma from his childhood led to the false identity he developed in his teenage years when he decided to rewrite his story and identity. He wanted to rid the world of those who had hurt him, and he'd almost succeeded before the prophecy of Harry's birth stopped and eventually destroyed him.
The circumstances of Voldemort's birth -- and the inability of the Muggle world to give him a family even in the absence of his birth parents -- resulted in the young Tom Riddle growing up alone and believing that the world was a cruel place.
He was eventually forced to accept that his father was the Muggle parent, and that his mother was the magical one. It was around this time that Riddle gave himself the alias "Lord Voldemort", to spare himself of the reminder of his "filthy Muggle father".
So, throughout the stories of Harry Potter, Voldemort's acts of terrorism and dark magic, the many breakings of his soul, and the methods in which he chose to be resurrected, had caused his appearance to drastically change as a direct result of what was in his heart: evil.
In spite of being Pure Evil as well, Lord Voldemort's evilness is slightly toned down in the film series, as the flashback scene of the orphanage from Half-Blood Prince has him admit that he only does bad things to the people who are mean to him (implying some orphans bully him) as opposed to the books where he admits ...
The REAL Reason Voldemort Became EVIL - Harry Potter Theory
Who is more evil than Voldemort?
Dolores Umbridge is. She's among some of the nastiest characters in the whole series (along with Fenrir Greyback (ew)). In some ways, she was definitely more sinister than Voldemort.
By Harry Potter and the Deathly Hallows, it's a stretch to call Draco a villain anymore. We just watched — or read — him struggle to reconcile his choices and morals in The Half-Blood Prince. He can no longer justify his actions, and is far more aware of the evil he was born and raised into.
Family. Snape's family background is mostly shown in flashbacks during the course of the last three novels. Snape was born to Eileen Prince, a witch, and Tobias Snape, a Muggle, making him a half-blood (hence the name, "Half-Blood Prince").
After the deaths of her parents, Voldemort and Bellatrix Lestrange, Delphini is raised by Euphemia Rowle, who was not fond of her and allegedly only took her because she was offered a substantial amount of gold.
Notably, Voldemort appeared to be entirely unaware of this split, as he later created a seventh Horcrux in his quest to have six, and continued to target Harry Potter despite him now holding part of Voldemort's own soul.
In Harry Potter and the Cursed Child, it is revealed that Bellatrix gave birth to Voldemort's daughter Delphi in Malfoy Manor before the Battle of Hogwarts.
Delphi was conceived from a liaison between Lord Voldemort and Bellatrix Lestrange. She was born in March of 1998 at Malfoy Manor, shortly before the Battle of Hogwarts.
Mason Riddle is the Son of Tom Marvalo Riddle, otherwise known as Lord Voldemort, and the only American student at Hogwarts School of Witchcraft and Wizardry.
According to the wizarding journalist Rita Skeeter, in a list of Most Dangerous Dark Wizards of All Time, Grindelwald would miss out on the top spot only because Voldemort arrived, a generation later, to take his crown.
The prevailing theory has been that Voldemort gradually lost his nose (and humanity) throughout his life due to his exclusive use of Dark Magic. The more Dark Magic he tapped into, the less human he became both figuratively and literally. This was only amplified as he split his soul to create the Horcruxes.
In the play "Harry Potter and the Cursed Child," which has become part of "Harry Potter" canon, it was revealed that Bellatrix conceived a child with none other than Lord Voldemort.
It is assumed Bellatrix was at least initially drawn to Lord Voldemort because they both believe in an ideology that favors pure-blood wizards and witches over other members of the community. This elitism, shared by the Malfoy and Lestrange clans, was instilled in Bellatrix since childhood.
The movies follow the books closely enough that they aren't really separate universes, except for the fourth movie. There isn't any truly compelling evidence that Snape is Harry's father, because all the points you raise are explained. Snape hated Harry because Harry reminded him of the man who "stole" Lily.
For the second time in Voldemort's life, the unforgivable curse rebounded on him, as the Elder Wand wouldn't kill its master. Since Harry and his friends had already destroyed all of Voldemort's Horcruxes, this finally ended Lord Voldemort's life, with Harry finally defeating the Dark Lord.
Although he wasn't turned into a werewolf, he did develop some wolfish tendencies such as a liking for very rare steaks. He married Fleur on 1 August 1997, although their wedding was disrupted by the arrival of Death Eaters following the fall of the Ministry of Magic.
Draco's belief in the superiority of Pure-Blood status influenced his prejudiced behavior, including calling Hermione a "Mudblood," but he eventually sought redemption by breaking away from the Death Eaters and saving Harry's life.
Malfoy was born in a pure blood family and had no doubt heard of the baby who defeated Voldemort, which would have intrigued him. Therefore he tried to befriend Harry, but came off as rude, which got him rejected. He then proceeded to bully Harry and his friends to avenge the rejection.
Voldemort intended Draco to die in the attempt to kill Dumbledore so that Lucius would be punished for his failure to retrieve the prophecy from the Ministry of Magic.
