She stole Visions corpse and revived him even though he was ready to die, only to fool him into being with her. She subjugated an entire town, which both took away their lives and put them through a lot of pain(as shown by the dude at Visions workplace). She kicks anyone she doesnt like or that challenges her in any way out of her false reality with no regard for their safety. She seems to be aware of what shes doing. Both Vision and Monica have brought it up to her but she chooses to ignore them. She left the hex on exactly one occasion when she took the missile back to the commander and made the barrier thicker. She left the hex purposefully to taunt the military, which means shes aware of the damage shes causing but does it anyway just to be with Vision. Other people died and their loved ones never did this.
Combine that with the fact that I think Wanda is stupidly OP and that I just think shes an annoying character plus having a general dislike of her before the show even started that I could never put my finger on, and it all culminates in me hating her with a burning passion.