In most cases, it is legal to watch fanfiction. Fanfiction is generally considered a form of derivative work based on existing intellectual properties. As long as it's not being sold without permission or used in a way that violates copyright in a major way, just reading or watching it for personal enjoyment is usually okay.
Fanfiction.net could also be a place to check. It has been around for a long time and hosts a vast amount of fan - made stories. However, the interface might not be as modern as some other sites. But still, it's worth a shot to search for your desired Dante vs Bayonetta fanfiction.
Asta is still alive in the manga. The story keeps evolving with him at the center of the action. There have been many difficult situations, but he manages to overcome them without dying.
Asta and Yuno are childhood friends in a magical world. They both strive to become powerful wizards and fulfill their dreams. Their paths are filled with challenges and adventures.