Warning: contains spoilers for Fantastic Four #45
In the midst of Marvel's Reckoning War, Fantastic Four's Reed Richards makes the ultimate sacrifice that he miraculously manages to return from. The war in question is the biggest event to happen in the history of the Fantastic Four, set up over a period of 15 years. It centers around The Reckoning, formerly the once peaceful Proscilians, who use technology given to them by The Watchers against them by initiating an all-out assault against the entire galaxy.
To put a stop to the war, Reed Richards absorbs all of Uatu the Watcher's knowledge and power into his own brain at the cost of an upgrade that's destined to kill Reed Richards in a manner of hours. Before the powers of the Watcher have time to take full effect on Reed's human brain, he uses his newfound insight on how to defeat The Reckoning by using the Ultimate Nullifier to stop them before they could access the Apex of all Reality. Doing so would allow them to destroy the entire multiverse. Reed succeeds, seemingly at the cost of his life.SCREENRANT VIDEO OF THE DAY
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However, in the opening pages of Fantastic Four #45 by Dan Slott and Farid Karami, Reed awakens from his supposed death. He instantly remembers that the Nullifier was originally designed by The Watchers to only be used by a Watcher. By absorbing Uatu's powers, Reed Richards had momentarily become a Watcher. Firing the Nullifier was enough to draw out all of The Watcher's energy, thus taking away the very energy that would have killed him in mere hours, reverting back his humanity. The Nullifier killed Reed Richards the Watcher, but not Reed Richards the man.
Reed Richards' "death" in the previous issue is more of a symbolic one than a literal one. Initially, he keeps his condition and near death as The Watcher a secret from his compatriots in the Fantastic Four. Once they find out, they naturally feel betrayed by Mister Fantastic. In between this and Reed learning in the same issue that he's forgotten how to cure Johnny Storm's Human Torch ailment, Reed's latest failings as a leader have been evident.
The symbolism here is that retaining his humanity could also suggest a regaining of moral compass for Reed Richards, or at least a desire to be better. The conclusion of The Reckoning War and Reed Richards' near-death as a result of it surely taught the leader of the Fantastic Four a lesson that will likely lead to a compelling redemption arc in the future.