There should be a post or two about Alois but none of the characters you mentioned. I’ll post them if I see any yandere fanart.
"I thought you wanted to be with me..?"
yandere killua getting offended by mito’s protectiveness…..
There should be some under #shingeki no kyojin.. not much since the fandom’s yandere focus is often on Mikasa and I haven’t found a lot on tumblr, but some at least.
If you have not read ‘risou no kareshitachi’ you need to.
We don’t have any general masterposts as far as I remember, but here are some yandere lists that I could find! If anyone knows any others, feel free to send me a link.