I'd say tag it as Original Percival Graves, and mention in the notes that your characterisation of Graves is darker than most people seem to headcanon him, just like you've explained here.
Popular fanon isn't canon. Graves is still a mostly unknown character, and your darker Graves is every bit as valid as anyone else's Graves headcanons.
Re: Advice on AO3 character tags?
(Anonymous) 2017-01-22 09:06 pm (UTC)(link)Popular fanon isn't canon. Graves is still a mostly unknown character, and your darker Graves is every bit as valid as anyone else's Graves headcanons.