Modern Day Grendel

Whenever I think of Grendel, I think of him as a person more than a monster. I kind of believe that something has happened in his past that has made him become the person he is. Sure, he can be from Cain's bloodline, but it still doesn't mean that he can't be good.
Someone that reminds me of Grendel is Accelerator from the Toaru Kagaku no Railgun and the Toaru Majutsu no Index series (If you plan on watching the anime, don't read any further. I am going to put so many spoilers. You should watch it anyways.) He was first seen as one of the main antagonists, but slowly became one of the protagonists. Accelerator was introduced as the highest level 5 esper in Academy City, a place where mainly students live so they can improve their Psychic abilities. The purpose of Academy City was to create a level 6 esper. There was an experiment that involved killing exactly 20,000 level 3 clones of Misaka Mikoto, who is one of the level 5 espers (There are only 7 in the entire city.) He was able to destroy a majority of them until he was defeated by Touma, the main protagonist of the Toaru Majutsu no Index series. Accelerator then has some sort of mental breakdown. As he later finds out that they are trying to make the clones stronger in level so he can level up to 6 more quickly, he meets Last Order, who is considered a failure and is the weakest of the clones. He couldn't kill her and instead protected her until the very end. He ends up getting shot in the head trying to protect Last Order, making his esper abilities rely on a battery in order to fight. His past was soon revealed. He was taken to Academy City at a very young age and was discovered to have incredibly extraordinary powers. Due to this, many people have feared him and even tried to kill him. Since he was really strong as a child, he was experimented on by many scientists. He soon turned into a cruel sadist. When he meets Last Order, she claimed that he was trying to warn all of the other clones (they get smarter and smarter as he kills each clone because their brains synchronize with each other) that he was going to kill them and that they better get away. Accelerator even goes to say that "I’m the Strongest Level 5, I don’t need brats worrying about me. Listen, even if someone is suffering before you, the kind of person that can take up arms without hesitation to shoot down the villain is no better than a villain himself. The kind that doesn't care about others, doesn't give 2nd chances; someone that kills if given a reason, is definitely not a hero. You don’t have to become that kind of person. That’s my specialty. Only I have to go through that," which goes to say that he really wasn't a bad person from the beginning, but was pretty much created. I think the same goes for Grendel, but since we haven't read the story yet, I can't say for sure.