Harry might use his wits and the environment around him while in captivity. For example, if he's held in a place with magical artifacts, he could use them to his advantage. He could break the chains that bind him with a spell - enhanced object and then make his way to Voldemort and defeat him.
One possibility is that Harry has discovered some long - lost connection between them that he thinks can be exploited. Maybe he's found out that Voldemort has some knowledge or ability that is crucial to solving a problem. For instance, if there's a prophecy that only Voldemort can decipher, Harry might approach him for help, despite their long - standing enmity.
Yes, there are likely fanfics out there with such a wild and unorthodox concept. Fanfic writers often come up with very creative and out - of - the - box ideas, and this is definitely one of them. It goes completely against the established canon of the Harry Potter series, but that's the beauty of fanfiction. It allows for exploring different 'what - if' scenarios.
Harry could become more powerful in a way that scares his friends. Voldemort's training might focus on the Dark Arts, which are powerful but dangerous. This could change Harry's magic style. He may become more solitary as his new skills and knowledge set him apart from his Hogwarts friends who follow a more traditional path of magic.
No, Joker wasn't the one who killed Batman's parents. The culprit was a common criminal during a mugging incident. However, Joker has often taunted and tormented Batman about this tragic event in their confrontations.
In most mainstream comic continuities, the Joker didn't kill Batman's parents. It was a random act of crime by ordinary criminals. But there might be alternate or non-canon versions where this could be different.