One of the most interesting aspects of Crisis was the fact that the Anti-Monitor was a really convincingly creepy dude. He didn't suffer from most of the weaknesses from which big-time super-villains usually suffered, because he wasn't in the least bit human. He liked to declaim dramatically, sure, but if he had his druthers he would have destroyed the whole positive-matter multiverse without ever having encountering a single superhero. He didn't want to defeat the Justice League or humiliate them or even to destroy them specifically - he just wanted them to be annihilated, to cease to exist and to leave no traces of their passing. Living beings in the positive-matter universes were less than dust to him, simply obstacles between him and the fulfillment of a billion-year destiny.
Accordingly, the one Achilles Heel in his plan was the fact that - while he was certainly more powerful than even the mightiest hero - he nevertheless hoped to avoid the inconveniences of physical confrontation. After six issues of successfully keeping the heroes at bay, he was surprised when they actually mounted an assault on the anti-matter universe in Crisis #7. He underestimated the power of the Kryptonians - Supergirl in particular - and suffered grievous harm when her blitzkrieg assault almost completely destroyed his containment armor.
It's not as if the Anti-Monitor had been ignorant of the threat the superheroes posed: on the contrary, he was fully aware of the danger. He had believed, however mistakenly, that he had already crippled their ability to respond by doing two things: first, he recruited the Psycho Pirate and used his emotion powers to keep the heroes of the surviving worlds off-balance by forcing them to fight each other; and second, one of the very first things he did was to kidnap the one hero with the power to travel easily between the multiple earths: Barry Allen.
Lots of pictures under the cut!
As I mentioned previously, it had been a rough few years for the Flash. He had seen his wife Iris murdered by Professor Zoom, tried for Zoom's murder, found guilty (it was a fixed trial), before finally being reunited with Iris in the 30th century (because, er, she hadn't really been dead). It was a confusing and disheartening period that took the hero about as far as he could go before he finally snapped. The end of the "Trial of the Flash" storyline left the character and the franchise exhausted, teetering right on the edge of the Crisis and his by-then-inevitable demise.
At the outset of the Crisis, the Anti-Monitor captures the Flash and gives him to the Psycho-Pirate as a plaything. This is one of the most disturbing subplots throughout the entire series: the Flash is repeatedly tortured by the Psycho-Pirate, forced to relieve his greatest fears and despairs, completely helpless to free himself. The Psycho-Pirate has come completely unhinged at this point, unable to restrain his most cruel and sadistic tendencies.
As bad as the Psycho-Pirate's torture has been, once free Barry is nonetheless able to dig deep inside himself in order to find a wellspring of strength with which to resist. For Flash fans, seeing their hero rise up and finally confront his tormentor after months of systematic humiliation was - in the immortal words of Dave Campbell - a "Fuck Yeah!" moment if ever there was.
The Flash had been pushed almost to the limit of human endurance, but he hadn't crossed over that line just yet: he won't kill the Psycho Pirate, no matter how badly he's been abused. The Flash isn't out for revenge: he's ready to fight back, and he's got a plan to dismantle the Anti-Monitor's entire military apparatus in the blink of an eye.
With the Psycho-Pirate's "help," Barry successfully turns the Anti-Monitor's own army of elite Qwardian Thunderers against him. The ensuing fight not only destroys a large part of the Qwardian army, but successfully distracts the Anti-Monitor while Barry attempts to figure out exactly what the villain is actually planning.
The Anti-Monitor isn't stupid. After having been thoroughly chastened by his battle with Supergirl, he's had enough of these distracting little insects: it's time to get rid of Earth - all five remaining Earths - in the most efficient and definitive manner possible: by blowing them out of the sky with a giant anti-matter cannon.
Barry sees the cannon and quickly ascertains that he doesn't have a lot of time in which to prevent total disaster. The mechanism itself is - as far as comic-book physics goes - brutally simple: it's a giant ball of anti-matter set to be catapulted in the direction of the Earths. There's only one thing Barry can possibly do in the moments left to him: run fast enough to disrupt the flow of anti-matter energy, thereby demolishing the weapon from the inside-out.
What strikes me the most about the character deaths in Crisis, two and a half decades on, is just how much deep respect these characters commanded on the part of the creators. Barry Allen was Mr. Silver Age, a historically important and universally beloved character - if perhaps not the most popular in 1985. But regardless of whether or not he was "cool," he still wasn't going out like a punk. The only thing big enough to kill Barry Allen was a threat so large that the entire universe was in mortal peril.
He isn't murdered. He's doesn't even die in battle. He dies by running as fast as he can in order to save the universe. It's funny that Barry's last story - or, at least, his last real story for a couple decades - would go on to be regarded as one of his best stories, but it's not hard to see why. The same holds true for Crisis #7 and Supergirl: both characters die doing what they do best, saving lives and protecting the universe from danger. It's such a simple concept, really: a hero should die a death commensurate with their heroism. The petty, ugly deaths suffered by so many superheroes these past few years communicate little aside from a general and pervasive contempt: a contempt for both the readers who become invested in these characters, and the characters themselves.