I made a list of anime that had proper closure so you wont need to go read the manga or novel. Most of them are Originals which are almost all of the time, have a proper ending and some even may get a sequel announced.
This is an incomplete list so please tell me which ones I missed and which ones to remove if any.
Thank you
Here's the link: https://theotakumeme.com/blog/complete-anime-manga-series