The third comic: #527 Watchmen
One of Alan Moore's major works, this is one of the comics I had read before. I'm not sure I quite appreciate how revolutionary it was, with retired or down on their luck superheroes, set up more realistically, seeming to be something we see more often. The commentary is clear in the work, not believing in the unambigiously good superhero, but the exploration of the different attitudes 'after the work ended' is as interesting. Not everyone is a good person anymore, and just as often the small bits are ignored in favour of the greater good. An amazing thing to have read.