#1
Crush) always had a crush on (oc) ever since (s)he met them (oc) didn't return the feelings

(Possible Hanahaki Disease sernario)

#2

(Oc) caught (crush)  killing (second crush)

#3

Crush) cheats on (Oc). They end up having a argument and (Crush) calls (Oc) useless and says that they never loved (oc). (Oc) yells "Maybe you'd be happier if I died then!" Out of anger (crush) yells back "Yeah, I would!