Everyone loves a hero who never gives up in the face of adversity. Who never backs down, no matter what the world throws at them. Well, sometimes the world has other plans.
Whether because a different writer has a different idea for how the character should progress or generally work, or because certain events are just that shaking, some superheroes just feel it's best to throw in the towel. Sometimes they come back, sometimes they stay gone for good.
And these moments can be built up over years to the point where you're just counting down the days until they throw in the towel, or in this case, they come out of nowhere and leave you utterly floored. But, just because you didn't see them coming doesn't make them bad, if anything it makes the act of them quitting even more effecting.
As long as you do it well, a superhero giving up can be the most emotionally resonant scene in your entire series. These moments range in terms of quality, but they are definitely the most shocking moments when our favorite heroes just gave up.
10. Superman - Superman #296 - #299
Being the most powerful superhero in the DC universe, naturally the idea of Superman retiring and the world adjusting to that retirement is a fascinating idea to explore. Equally fascinating, in this case, is focusing on how Superman himself would adjust to his own retirement. This is, after all, a guy who doesn't have an unhelpful bone in his body.
However, at some point he decided to at least give being Clark Kent full time the old Kryptonian college try. In Superman #296, Clark starts noticing an anomaly: whenever he changes into his Clark Kent persona, he loses his powers completely (caused by a villain who was fluctuating his powers, long story). He decides to test the theory by straight up abandoning the Superman identity altogether and becoming Clark Kent permanently. Even managing to finally work out a serious relationship with Lois Lane that lasted long after this story.
Superman even goes so far as to ignore someone in trouble because the police are already on their way and have it handled. But of course, the big lovable boy scout can't stay away forever, gets the anomaly worked out, but at least gets to keep his relationship with Lois.
But still the decision to quit being superman for almost four issues was a bold experiment on DC's part.