In what is quite easily the single most fucked-up (and probably saddest) Undertale fanfic so far, Flowey goes inside Alphys' head and takes control over her brain, eagerly seeking his revenge for what Alphys did to him and his mother in the previous stories Motherly Fuckery and Incestual Apocalypse.

How, you may ask? Why, only by doing infinitely WORSE things to HER in return, of course, including but not limited to making her actively destroy everything she loves and holds dear to her and quite literally torturing her to freaking DEATH!

You know, for KIDS!