Sure. Kylo Ren was Ben Solo. He went bad because of Snoke's influence and became a key figure in the First Order.
Kylo Ren was originally Ben Solo. He was the son of Han Solo and Leia Organa. Ben was strong in the Force but was seduced by the dark side. Snoke took him under his wing and trained him to be a powerful Sith - like figure. He then took on the name Kylo Ren, causing much pain to his family and getting involved in the conflict between the First Order and the Resistance.
Snoke was a major figure in the First Order. He had an interest in Kylo Ren and trained him. His own back story wasn't fully detailed, but he was a significant threat in the Star Wars story.
Sure. Rosalina was a girl who found a Luma and then journeyed through space, eventually becoming the caretaker of the Comet Observatory.
Grindelwald was an important figure in the wizarding world's history. He was once a promising young wizard. But he became power - hungry. He thought wizards were superior and should rule, which led to his dark deeds.
Casper's back story in brief is that he was once a human boy. After death, he turned into a ghost. However, he is different from other ghosts as he is friendly towards humans.
Kuromi is a Sanrio creation with a back story of being different. She's a bit of a troublemaker, and her story is centered around her non - conformist attitude compared to other Sanrio characters, especially in relation to My Melody.
Hodor was originally Wylis. When Bran was in a dangerous situation, he warged into Hodor's mind. This event somehow damaged Hodor's mind and left him only able to say 'Hodor'. It was a tragic event that changed Hodor's life completely.
Sure. Catwoman, Selina Kyle, often had a tough upbringing in Gotham. This led her to a life of stealing.
Sure. Selina Kyle is Catwoman. She grew up in hardship and turned to thieving. She's known for her cat - like skills and has a complex relationship with Batman.
The Terrifier is a horror icon. His back story has elements of him being a deranged and violent being. Not much is clear about his origin but he is known for his extreme acts of brutality.