>>280208653
Hare + Guu definitely
One of the very few cases I know
I read the manga after watching it just to see the difference and even besides having a really bad TL, it was just noticably more amateurish (understandable as it was the mangaka's first serialization)
The anime basically took 90% of the meat of the manga, rearranged a lot of stuff, added some content here and there, adjusted some scenes (up to changing which characters a scene happened to) and in the end made a much better story out of it, much more coherent.
Masterwork of adaption I'd say.
Also adding in Guu's movements and voice was a huge bonus.