Captain America Just Took The MCU's Most Iconic Line To The Comics
Warning! Spoiler for Avengers #40 below.
Captain America will never give up fighting for what he believes in - it's why one of his most iconic MCU lines is "I can do this all day," when he's in the face of great adversity. Now, Steve Rogers is using that mindset in the comics, as he's forced to square up (reluctantly) against Doctor Doom in a battle for the Phoenix Force.
The first mention of the iconic line in the MCU came from Captain America: The First Avenger, when the pre-Super-Soldier Serum version of Steve gets beat up in an alley and uses the line in response when he's told that he doesn't know when to give up. He also uses the line when captured by Red Skull. In his fight against Iron Man in Captain America: Civil War, he utters the phrases in a battle against his former teammate. Lastly, when fighting a past-version of himself in Avengers: Endgame, the line is used in a more comedic manner. The line personifies Captain America's attitude to never give up.
In Avengers #40 by Jason Aaron, Javi Garron, and Leinil Francis Yu, Captain America finds himself up against Doctor Doom in the Phoenix Force's competition to choose who will be the next host of its massive cosmic powers. His battle against Doom doesn't go particularly well, as the power-hungry villain is desperate to claim the powers of the Phoenix. Both characters get fiery upgrades and when Doom unleashes a massive blast and throws a huge dinosaur skull at Cap, he declares himself the winner. However, Captain America gets up and says his iconic line, telling Doom, "I can do this... all..." before getting hit with another blast.
In a surprising twist, despite being engulfed in flames and seemingly killed, the Phoenix Force keeps Steve alive. Doom, frustrated that he can't win the fight by killing Captain America, forfeits, as he says the Phoenix is looking for a host that's clearly not him. The fight ends with Captain America being teleported into a blank plane of existence holding a number of Marvel heroes who are about to participate in their own fights.
Captain America's death and revival at the hands of the Phoenix Force is the most extreme example of the mindset behind his MCU line. Despite getting overwhelmed and eventually killed (in a way) in the battle, the Phoenix Force saw his perseverance and heroism as a reason to keep letting him fight. It seems to win the power to host the Cosmic juggernaut, winning a physical battle won't be enough - in this case, Captain America's resolve was key to getting Doom to forfeit. Avengers #40 is in stores now.