Ada Wong (Capcom 30th Anniversary Book)
"Sultry spy Ada Wong burst into the Resident Evil series in the game's second installment, and she quickly became a fan favorite. She first appeared as a supporting character, but went on to be playable in post-game bonus scenarios of Resident Evil 4 and Resident Evil 6, and she's frequently playable in the series' famous Mercenary Mode.
[...] She's worked for some unsavory characters, including Albert Wesker, but just as frequently double-crosses them for other, more shadowy factions. Ada has worked her way into the hearts of dozens of men, including several Umbrella employees and frequent Resident Evil hero Leon S. Kennedy.
It isn't clear whether she ever reciprocated their feelings - she does seem to honestly care about Leon, saving his life in nearly every game in which the two appear. But maybe that's all just part of her long con?"