Except that in real life, if you meet a girl who constantly protests that she wants nothing to do with you, it's because she actually wants nothing to do with you. "Sporty girls" actually exist; "tsunderes" as we know them are largely an invention by creeps who want an excuse to deny it when they've been rejected.
That's the tsundéré cliché. The tsundéré archetype is basically a character (usually female) who can be harsh or bitter (tsun-tsun) or sweet (dere-dere).
The next time you call me "tsundere", I'll kill you.