Warning! Spoilers ahead for Heroes Return #1
In the finale for Marvel's Heroes Reborn, it looks as though Marvel's version of Batman has been set up to become a major threat for the Avengers in the near future. In the event's conclusion, the Avengers reassembled despite President Phil Coulson having altered reality in his own image, changing history so that his Squadron Supreme of America became Earth's Mightiest Heroes instead. However, Coulson's reality - made in service to his master Mephisto - was still destroyed and the original Marvel Universe was restored. However, the SSA's Nighthawk has vowed to bring his world back, which can't bode well for the heroes who took it away from him.
The Reborn saga culminates in Heroes Return #1 from writer Jason Aaron and artist Ed McGuinness which shows readers that the Avengers and Squadron Supreme had an epic battle, effectively being a new Avengers vs. Justice League event seeing as how the Squadron Supreme of America have long been depicted as counterparts to DC's superteam. While President Coulson tried to use his Cosmic Cube from Hell given to him by Mephisto to destroy the Avengers for good, the combined forces of the new Phoenix and Starbrand were able to use the Cube's power to restore their world as it was meant to be.
While the Avengers effectively took down the SSA before the world was restored, Nighthawk ended up being the last of Squadron standing, and he wanted to make sure they knew that before reality was reset: "I want you to remember this too. How we made this world better. Safer than you even could. And remember that despite everything you did to stop us, in the end...I was still standing." Additionally, the end of the issue confirms that Nighthawk remebers the world of Heroes Reborn, and he's determined to bring it back somehow.
Out of all the heroes of the Squadron Supreme, Nighthawk should definitely not be underestimated, and it's pretty concerning that the Avengers don't seem to be actively tracking him at the moment. While an excuse could be that the majority of the Avengers don't remember the altered reality, Blade (and perhaps even Maya Lopez' Phoenix) do remember and could (and should) offer a debrief of what happened due to Coulson and Mephisto's Pandemonium Cube.
In any case, Nighthawk is a brutally determined, focused, capable, and effective individual, making him the equivalent of DC's Dark Knight. As a result, it's more than likely that he'll soon find a way to bring his world back, which will no doubt put him at odds with the Avengers once more. However, one can imagine that, given enough time to plan and prepare, Nighthawk could certainly find and exploit the weaknesses of each of the Avengers, just like Batman and his contingencies for the Justice League. Hopefully, the Avengers will be prepared as well when Marvel's Batman inevitably becomes their next big threat down the line.
More: Heroes Reborn Missed Its Chance To Be Bigger Than Marvel's Past Events