Is there any improvised manga adaptation that ended up being better than original?

I am looking for anything that might be similar to this scenario:

Example: An ongoing LN/WN/manga got adapted into something else (manga, anime, movie, etc). The adaptation turns out to catch up to the current chapter in original media faster than expected. Then the translation team has to improvise its own story (by branching off from the original to create its own conclusion). Surprisingly, the improvised story turns out better than the original's conclusion (when the LN/WN/etc) finishes.

I know that a lot of adaptation chooses the safer path with using fillers (like in Naruto, Bleach, Gintama, etc); therefore, if there is any, I am looking for another risky approach by the adaptation.

Sorry if it doesn't make any sense, I am just really curious