William wasn't truly Brainwashed.
Only his feelings were manipulated, so that he was more affectionate towards Pina.
Nothing else was changed about him, as he had all the decision making capabilities.
The reason Remilia is after William for revenge is because she knows how the Drug works (based on Emi's knowledge), and understood that William never really confirmed any of the allegations against Emi'Remilia properly, even-though he claimed to have loved her and knew her since childhood (aka., Remilia is angry because William gave up on the trust build by Emi'Remilia over a decade so easily).
Same to you: (copy pasted from my other reply)
Anyways, maybe brainwashing means something else to you, but to clarify:
"the process of pressurizing someone into adopting radically different beliefs by using systematic and often forcible means." (oxford dict.)
It is precisely what she did using love potions. Brainwashing is not about controlling someone like a literal puppet, it is by emotional manipulation (such as this) or similarly in real life using propaganda or seduction. You could argue about accountability, whatever. But he
was brainwashed.
Remilias anger is completely understandable to me and the point of my post is to say that she really is a villain - her actions clearly gloss over moral and details, she simplay acts out of spite. Besides: In the manga, which is the medium under scrutiny, she definitely did not consider his side, or any other side except her own. And whatever happens in the novel should not affect this discussion here.
