Well, firstly the drawing is amazing. I'm pretty sure you are already aware of your talent, so you probably want to know how well you captured Tifa herself.
You captured has muscles perfectly, imo. You didn't give her skinny arms, as she was a martial artist that clearly had plenty of strength, but at the same time you didn't go overboard and take the sexiness away from her.
Her chest seems to be more round. I remember it being very Triangular in the game. Though, it's probably good you didn't draw triangle tits.
The gear seems to be spot on of what I remember. The shading and colors are very great and detailed. I also love the way her hair covers one eye, but her uncovered eye expresses enough emotion for them both. The reason we all love Tifa, she is extremely sexy but you can see the toughness in her eyes.
I would like to see you draw one of Tifa mid-swing at an enemy. You might occasionally catch art this good in a portrait but rarely in an action shot.
first off, great work on the color scheme, really like the colors and shading and highlights of the picture but a few things were bugging me, this is all assuming you want a critique on having an anatomically correct figure
the first is how the arm is positioned, the arm on the left seems to be straight and the other is bent, i tried doing this, and it is a very uncomfortable position to have your arms in no matter what angle, so either the arm on the right has to be straightened out more, or the arm on the left needs to be bent a bit
the shoulder on the left seems to be a bit too... pointy, needs to be a bit more round because thats where the deltoid muscle is, and unless you're lifting your arms up from the side, it wouldnt crease like that
the jaw line is a bit lopsided cuz from drawing a straight line from eye to eye and bringing that down the face, you can see that the position of the jaw is not the same on both sides
the last two is a bit nitpicky but the reflection in the eyes is off cuz the light source is coming from the right side, and so the glare on the eye should also be on the right or at least the biggest glare, there can be the smaller reflected glare on the other side as well and the edge of the mouth is bugging me @.@ it feels like her lip curls up at the edges, i think you were trying to go for the crease when its against the cheek, but the shadows feel too strong there