Complex sentence: Meanwhile, the present Mr. Belt became corrupted by an evil chip Banno implanted (originally meant for Roidmudes) while kidnapping in episode 40 prior to the movie, thus pleading Shinnosuke to destroy him to prevent the dystopian future.
Split into simpler sentences: Meanwhile, the present Mr. Belt becomes corrupted by an evil chip Banno implanted in him and he is kidnapped prior to the events of the film. This is why he pleads with Shinnosuke to destroy him to prevent the dystopian future.