Hmm. I always thought Lucy Lawless as Xena looked the part -tall, big-boned and sturdy. (NB, a man knows he's reached middle age when halfway through an episode of Xena he realises he's following the plot). Both Lynda Carter and Gal Gadot have the necessary statuesque build to get away with Wonder Woman, thankfully. Similarly, Queen Latifah is sturdy enough to pass muster as the Equalizer (though Edward Woodward had more style, but he's English).

Not sure about Black Widow, though.