Rachel
The other mentioned characters are huge factors in the game but no one character clearly stood above all others quite like Rachel. She was the DOA4 Busa, the Vanilla DOA5 Jann Lee. The undisputed and unchallenged best in the game, complained about from scrubs to even high level players simply due to the braindead tactics and mindboggling results from them. She has since been removed from prominence after the first patch, but during the early days of this game, there was no character with the impact, presence and sheer and utter dominance of Rachel.
There is no other, she was the character of 2013.