I'd say Alyx Vance for sure but let me throw out Lara Croft as well, I know as the games went on she mutated into some late 90's horror story but the first iteration (tomb raider 1 & 2) she had just the right amount of sass while the sequels just turned her into a bimbo. Compare the promo shots for Tomb Raider 1 where the focus is on her dual wielded Browning pistols to Tomb Raider 3 where the focus is on her plunging neckline.
Toby Gard who invented Lara Croft got kicked off the Tomb Raider team half way through TR2 as he continually objected to the hyper sexual representation of Lara as it was destroying her image. He was right, and after Core design when bankrupt after the 6th TR game, the American team who took over hired Tomb Gard right away and has been creative director from Legends onwards.