I guess 'Code Geass: Lelouch of the Rebellion' is the one!

'Code Geass: Lelouch of the Rebellion' begins in Japan, which is dominated by a fictional kingdom, the 'Holy Britannian Empire.' The protagonist is [Lelouch], a former Britannian prince, and as the title suggests, it's an SF robot anime about Lelouch rebelling against his homeland, Britannia. Code Geass starts when Lelouch obtains the power of absolute obedience, [Geass], from a mysterious girl named [C.C.]... I believe this story is best enjoyed by avoiding spoilers entirely, so I'll wrap it up here. People around me tend to dislike the unique art style and don't watch it, so I'm recommending it here 🙇‍♀️ I really recommend it, so please give it a watch!