Not only is she one of the most tsundere characters in anime history but probably the best tsundere ever!! That might be a little biased since I'm absolutely in love with her but who cares. How ever you look at it, they don't come more tsundere than Taiga-chan ^.^
"Relying on someone, helping each other out, and supporting each other. Most would say that's the right thing to do. However, that's just idealistic. In reality, someone always gets the short end of the stick"