Anime

How complete is the anime?

500

Thinking of watching 86 but before I start:

How much of the existing LNs does the anime adapt?
Is the anime expected to end in such a way that provides a complete story even if the LNs continue further? e.g. Suppose the story is about a war between X and Y. I'm wondering if the anime will show the resolution of the war between X and Y (even though the LNs have X fighting Z later, etc.). Would kinda suck if it ended in a cliffhanger though.

Decretum 4y
there are 9 total volumes and we are now at the end of vol3, we wil probably end on a good part of v4 or the v3 epilogue
Niounomiya 4y
Part 1 adapts the entirety of the first volume, while part 2 adapts the 2nd and 3rd volume.
There are currently 10 volumes released and the story is ongoing.
As for your second question, it's kinda complicated. The story was originally going to end on volume 1, but the author won an award and decided to continue the story. So, in a way, you can take part 1's ending as an ending to the story, but that's not recommended, because part 2, especially episode 22, is peak.
Also, the anime doesn't offer an original ending, if that's your question. It is completely loyal to the LN and is considered to be one of the best recent LN adaptations.
The last episode's not released yet, but I don't think it's gonna end on a cliffhanger.