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.