Is there a manga where we have a yandere loli? preferrbly yandere little sister but anything is fine EDIT: The Yandere characters has to be a loli, not high-schooler and above.
Higurashi No Naku Koro Ni is basically filled with psycho lolis. There is also one, iirc, in Jinrui wa Sutai Shimashita (tho not sure if it has a manga), and one in Deadman Wonderland (not the two-faced girl but the one with a hammer). Youjo Senki’s mc is a sociopath loli.