My choice: Re:Zero (web novel)
The best thing about Re:Zero is the immense psychological depth of the main character and his character development. It might feel like he can't possibly grow any further but the character development never stops
As for my favourite thing about Re:Zero, it is the presence of incredible mysteries and the complex lore surrounding it. I also love the fact that it incorporates many genres and switches between them seamlessly (psychological thriller, drama, mystery, action, romance, psychological horror)
It has hundreds of side stories and What If stories that flesh out the world and lore really well
by ripterrariumtv