A good ending is the single most important part of any given comic. It doesn't even matter if the rest of the comic is absolutely golden - a bad or unexciting ending can totally ruin the overall comic, and worse, put you off getting any more of that particular series.
With the last moments of a comic being the first moments that tend to leave a lasting impact, the pressure is on comic creators to make both their individual comic issues and overall comic titles end on impressive notes.
With so many comics containing absolutely mind-blowing moments in their actual main plot, it's wild to think that they manage to make endings that continually amp up the tension and drama of the series for issue after issue. Even in their closing moments, many comics manage to end on a note that would have made it worth reading a story you hated just to just to get to its insane ending.
With even secret alien clones and impossible alternate universes not ranking among the most impressive comic endings to date, it could be argued that a near-impossible standard has been set - much to the collective benefit of comics fans everywhere.
10. Ric Grayson
Proving that nothing is ever truly sacred, Batman #55 proved that DC were pronouncedly frightened of having a character go by the name of 'Dick' in 2019, as they rebooted the character entirely by having him shot in the head and subsequently gaining amnesia in what appears to be a monumental change to the character developed entirely so they can start calling him 'Ric' instead.
From this point onwards the entire character of Nightwing totally changes - including in the actual Nightwing comic, wherein the fiftieth issue starts with a basically rebooted Ric with very little explanation, which is likely to have confused its fair share of Nightwing fans who weren't up to date with the main Batman comic itself.
Not all insane comic endings lead to good changes, and this may just be the best example of this in recent history.