I know she was undefeated and everything, but I don't think calling someone an all time great boxer among females means very much, does it? What other legends of the sport did she beat? I'm not making fun, I genuinely have never heard of any real life female boxers outside of the Olympics, so I'd like to know. Serena's last decade of generally beating up on no hopers might not mean much, but she proved herself a genuine all time great about 16 years ago.
Now in the pantheon of great American female athletes I'll go with Caitlyn Jenner. Watching a woman beat the crap out of all those dudes in decathlon for like 4 straight years, and set the world record about 3 times was just awe inspiring.