Tifa is a hopeful and kind girl. She's strong, tough and loyal to those she loves. But she's human and she's flawed. Much like everyone else, which is why people can relate to her. She's shy when it comes to love and took a back-seat when Aeris came into the picture. She almost instantly developed a friendship with Aeris, even still when Aeris admitted she liked Cloud. Was she bitter towards Aeris? Hateful? Certainly not. That just wasn't her personality. Aeris was her friend and that seemed to come first. Even after Aeris died, Tifa didn't pursue a love relationship with Cloud. (Even two years later, Tifa has not forgotten her friend and wears a pink ribbon in memory of Aeris.)
Tifa haters often use the excuse "she's a slut!" as to why they dislike her. But let's handle this in a mature way, shall we? Tifa was most certainly not a slut (this goes for Aeris, as well). Not once did Tifa ever throw herself on any man, not even Cloud. She's shy; she is reluctant to admit her feelings towards Strife. Is it the outfit that makes people think she's slutty? She's a martial artist. It's only logical that she wears clothes that are comfortable to fight in. The skirt, however, is another thing entirely. The creators of Tifa's character could have easily put her in pants, or even shorts, but they chose not to (meh, men). That's not the character's fault. It's a ridiculous reason to hate Tifa, simply because of her oufit.
Some people often use "depressive" and "tragic" to describe her, insisting that because of her responses to certain situations, Tifa must be a very pessimistic character. I see this in a very different light. Her reactions are very normal to someone in her situation. Actually, considering everything Tifa had went through, she is very well-balanced. She had been through the death of her mother, years later her father, her friends and her town. She lost Cloud to Mako poisoning, but did she give up? No, she sucked it up and helped Cloud find himself; in fact, if it hadn't been for Tifa, Cloud would have been lost when they fell into Lifestream. In there, she had been lost and alone in the darkness of Cloud's memories, yet she had found the strength to keep going. Throughout the game, Tifa gives encouraging words to her Avalanche family and her new friends, often telling them not to give up and to fight. If most people had been through what she had, they would have curled into a fetal position and bawled their eyes out.
Tifa values friendship above all else and would gladly fight for her friends (which are also her only family).
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