Perhaps its because I have Avengers on the brain, but I loved this Black Widow cosplay by Rayi-kun. Rayi is a cosplayer out of Germany, and while she has many costumes in her portfolio I think Natasha is my favorite. Black Widow's core uniform is pretty much just a black jumpsuit, so it's always all the extra accessories that seperate the good renditions from the average ones. She's done a great job with those small details, from the Shield patch & Widow logo to all the belts and pouches, she recreates the film version of Black Widow to a tee. Of course, the red hair doesn't hurt either.
It would be wrong however not to mention the amazing job that Franky-Chan & Daishota did with the photography. The costume is spot on, but bad photos can make or break a cosplay, and all the shots here are stellar. The ones featured above and below are my favorites, but you can catch more photos here & here.
Rayi-Kun has done a number of different cosplays ranging from Final Fantasy to Belle (of Beauty & the Beast), so if you like her stuff make sure to let her know.