Characters must be from either DC or Marvel
"In a torture chamber beneath Paris, I had all that ignorance stripped away. I learned what it felt like to run thirty-six miles with four broken ribs and lungs burned by tear gas, to climb six stories with a dislocated arm and a ruptured achilles, to endure seven days of nonstop electro-interrogation and sleep deprivation and water boarding.
I left Gotham thinking I knew how to hold my own in a fight. In a boxing ring in Serbia, I had that overconfidence beaten out of me. I learned how to fight with a concussion, blind and deaf, even standing in a puddle of my own blood. I left Gotham a soldier, believing I knew how to survive.
And then I crossed the Sahara on foot, living off insects and snakes and a teaspoon of morning dew. I left Gotham believing I knew depravity, as if watching the nightly news or trolling true crime blogs could somehow tell me all I need to know about inhumanity."
I don't know if she's the toughest, but Batwoman seems pretty tough.
From DC I only really see WW and maybe Earth 2 Hawkgirl (even though I have admit to not keeping up with it that well).
Marvel has a lot on of strong females right now with Capt. Marvel, Storm, Capt. Universe, and all of Brian Wood's X-Men cast.