Thaddeus "Thunderbolt" Ross has grown to have a unique role in the overall Marvel Comics canon, transforming from a supporting character of the Hulk to a superpowered being in his own right. Since 2008, Ross has been best associated with his tenure as Red Hulk, a much more aggressive take on the Green Avenger. In recent years, Ross' involvement in the Marvel universe - both as a civilian and as Red Hulk - has shifted wildly, with him faking his death going underground, leading to Captain America being framed for his murder. The recent events of the current Captain America series have properly brought Ross back into the fold -- and helped reawaken his red-hued alter-ego in the process. Spoilers for Captain America #26 from Ta-Nehesi Coates, Leonard Kirk, Matt Milla, and VC's Joe Caramagna below! Only look if you want to know!
The issue places Captain America and nearly everyone in his ensemble in dire straights, as they try to get an upper hand against the Power Elite. Part of the Power Elite's plan has consisted of kidnapping the Daughters of Liberty, who Ross has been secretly aiding in the time since faking his death. As the issue goes along, Ross is tortured by Crossbones and Cutthroat, the latter of whom is tasked with stabbing him with his sword. Surprisingly, Ross begins to ask for more force from Cutthroat's magic sword -- and as Misty Knight explains, there's a reason for that. Ross is deliberately using the power from the sword to rile up his anger, as a way of fully reawakening Red Hulk. Ultimately, Ross succeeds, breaking from his restraints and fully reembodying Red Hulk.
He jumps up to destroy a few planes being flown by the Power Elite, allowing Team Cap to rest a bit more safely. As Steve remarks at the end of the issue, Ross' return wasn't what he expected -- instead of being a personal ally or an adversary to Captain America, Ross chose to fight with them out of patriotism.
Red Hulk's return definitely has an epic connotation behind it, as well as the idea of Ross becoming more heroic - or at least, morally grey - in the Marvel universe. Especially with Ross' live-action role in the Marvel Cinematic Universe continuing to evolve - amid years of rumors that he could ultimately lead a Thunderbolts movie or Disney+ series - having him properly folded back into the canon is definitely a pleasant surprise.