If you don’t know what a “yandere” is, it is when a girl/guy is really gentle and loving at first but then becomes violent, which is entirely different than what a tsundere is.
My personal top 5 list of Yanderes are below!
#1: Sonozaki Shion (Higurashi no Naku Koro ni)
#2: Gasai Yuno (Mirrai Nikki)
#3: Kotonoha Katsura (School Days)
#4: Kaede Fuyou (Shuffle!)
#5: Sekai Saionji (School Days)