10 Comics Heroes Who Lost Themselves (But Saved The Universe)
7. Monica Rambeau - Avengers: No Road Home
The most recent entry on this list is also notable for being the only entry where the hero does not die in their sacrifice, but still loses a large part of themselves in the process.
Monica Rambeau/Spectrum gives up most of her power to save the universe, but still retains a small portion of it to be considered a powerhouse.
The ten issue series chronicles the Olympian night god Nyx's mission on wiping out her pantheon and covering the universe in eternal darkness. It therefore falls upon Rambeau, Hercules, Vision, Scarlet Witch, Hulk, Hawkeye and Rocket Raccoon to save all of creation from the darkness-driven deity.
The heroes are fighting a losing battle across space and time before they realize that the key to cementing Nyx's dominion lies within the House of Ideas, a realm that birthed every known object, person or idea in creation. Monica uses up most of her cosmic energy to enable Vision to enter the House, and he uses its power to create an army of heroes to defeat Nyx and put an end to her plans.
After the universe is saved, the light powered hero returns to her family and describes herself as mortal, noting that she is at a lower level of power than she was before.