In one of her darkest storylines, Captain Marvel was tasked with killing every member of the Avengers, a task she seemingly carried out to perfection–something for which she later received the ultimate payback.
Carol Danvers aka Captain Marvel was captured by a villain named Vox Supreme and was forced to kill her fellow Avengers in the storyline “The Last Avenger.” The brutal saga opens with Captain Marvel attacking Thor without provocation as the Avenger was minding his own business at the Avengers' base. The two engage in combat that spans across the entire globe until Captain Marvel finally gets the upper hand and proves to be victorious. The issue ends with Captain Marvel presenting Vox Supreme Thor’s severed head. The next issue reveals that Thor was fine, and the rest of the Avengers had nothing to fear from Captain Marvel as the head Carol gave to Vox was that of an incomplete clone of Thor that was decommissioned long ago. While hiding the Avengers in a pocket dimension for safety, Captain Marvel delivered the clone corpses of the rest of the Avengers to Vox Supreme until she was able to defeat the villain when he least expected it, proving that every Avenger Captain Marvel ‘killed’ was actually completely unharmed.
In Captain Marvel #32 by Kelly Thompson and Sergio Davila, Captain Marvel is minding her own business, flying through the air and considering her position in life, when suddenly she is attacked without provocation by a warrior who is wearing the same suit Carol wore when Captain Marvel was forced to attack the Avengers. Recognizing this as the villainous work of Vox Supreme, Captain Marvel doesn’t hold back when fighting this mysterious foe as she knows how powerful someone wearing that suit is bound to be, using herself as the prime example. While the battle was intense, Captain Marvel came out on top and swore to take down Vox Supreme once again.
While she won her battle against this mysterious warrior, the fact that Captain Marvel was attacked the same way she attacked every one of the Avengers is perfect karma especially because she wasn’t seriously injured or killed just as they hadn’t been. Even though Captain Marvel wasn’t going to kill the Avengers, she still had to attack them unexpectedly as Vox Supreme was watching Carol's every move, and she couldn’t reveal her plan to them until after she had beaten them to a pulp and brought them to the safety of the pocket dimension. So, getting the wind knocked out of her by a fighter in a Vox-suit is the ultimate payback for when she did the same thing to her fellow Avengers.
Captain Marvel’s assault on the Avengers was done in the best possible manner given the circumstances and her goal was never to kill them but to merely knock them unconscious until she was able to explain everything in a safe environment. However, those knock-outs seemed incredibly painful nonetheless. So Captain Marvel wasn’t entirely innocent in that scenario. So, whether or not she deserved it, Captain Marvel received the ultimate payback for ‘killing’ the Avengers.