Who kills Diavolo?

Could you elaborate on the context surrounding the question "Who kills Diavolo?"? Is this in reference to a specific work of fiction, such as a novel, comic book, or television show? Without more information, it's difficult to provide a precise answer. However, if we're working within the realm of speculative fiction, the identity of the killer is often a central mystery that drives the plot forward. It could be a surprise reveal at the end, or a character that has been hinted at throughout the story. The tone of the question suggests curiosity and a desire for information, so perhaps the speaker is looking for a spoiler or wants to discuss the implications of the reveal. In any case, more context would be needed to give a satisfying answer.