What's that? You've never even heard of the apparently-indestructible robot who's caused trouble for Marvel Comics' Avengers many times in his 40+ years of existence? Sit back and learn. Soon, you too will kiss his robot foot.
Who Makes Ultron So Great?
Well, firstly, just look at him. He's awesome. (And while we're at it, how can you not love a robot who talks like that?)
A product of the (occasionally overly-)imaginative Silver Age of comics, Ultron is much more than the average killer robot; his secret origin involves him rebuilding himself five times and then hypnotizing his creator into forgetting he existed, for one thing. Ultron first appeared in 1968's The Avengers #55 (following an in-disguise cameo the issue before) calling himself "Ultron-5, The Living Automaton" but, within a year, he'd already upgraded himself to Ultron-6 by coating his body in Marvel's unbreakable alloy Adamantium (Yes, the stuff on Wolverine's bones). That's the thing about Ultron; whereas other killer robots are content to just sit around on their metallic asses when not trying to destroy the world, Ultron is all about the self-improvement. Well, partially about the self-improvement, at least; there's also a pretty unhealthy obsession with his creator, Hank Pym and his girlfriend, Janet Van Dyne (AKA Ant Man/Giant Man/Goliath/Yellowjacket and the Wasp). According to former Avengers writer Kurt Busiek, it's that mix of self-refinement and hatred for his "father" that makes the character so wonderful:
Aside from Ultron being a really compelling visual design — there's just so much menace in that jack o' lantern face John Buscema gave him — he stands head and shoulders above other psycho killer robots because he's not just a killing machine. He's a robot with an Oedipal complex. All the coolest stuff about Ultron comes from there — the creation of the Vision (which also ties into Wonder Man's story), his complicated relationship with Hank Pym, his attraction to the Wasp and attempts to re-create her...the best villains are villains where there's a personal stake involved, and Ultron's a robot that's all about the personal. He's tied into the complex web of relationships that makes up the Avengers, and that right there makes him more compelling. Being murderous, indestructible, brilliant and obsessive just adds to the fun.
The Ultron Empire
As much a family man as a genocidal maniac, Ultron has also managed to surround himself with quite a collection of relatives throughout the years; he has built himself two "brides," Jocasta and Alkhema, both of whom have rejected him and went on to try and undo his various evil schemes, as well as two "sons," the Vision and the much less robotic sounding Victor Mancha, both of whom went on to become superheroes with the Avengers and the Runaways, respectively. It's a good thing he's obsessed with this supervillainy thing, because apparently he's not so great when it comes to creating obedient robots.
Ultron's Greatest Hits
Amongst some of Ultron's (admittedly momentary) triumphs:
* Turning Tony Stark into a woman by taking control of the Iron Man armor and doing something that was never really properly explained but had something to do with rewriting DNA sequences (Ultron seems to have a particular thing against Tony Stark; he's also re-assembled his body made out of old Iron Man armors and turned Stark into his "psycho-hypnotic" slave. Having a grudge against Iron Man can only be a good thing).
* Coming up with a plan to plunge the world into a "volcanic winter" by placing bombs underneath volcanoes around the world. I'm not entirely sure what a "volcanic winter" actually is, but I'm sure it'd involve a lot of lava, and it's hard to fault such a wonderfully James Bond Villain-esque ploy for style and ambition.
* Slaughtering an entire European state singlehandedly as a warning to the rest of the world not to fuck with him. Kurt Busiek can take credit for that one. He explained to me,
In going over Ultron's history in preparation for the story, it seemed like decades since he'd been a truly compelling menace — he'd been handled too easily, treated like a known quantity, so it didn't matter if he was kind of an afterthought in stories, or taken down without much difficulty. So we wanted to remind people of how dangerous he is, give him some impact to reestablish him as a deadly, ruthless threat.
* In the same story as above, creating an entire army of himself to populate the world... after killing all of humanity, of course. Busiek again:
In dealing with recurring villains, I tend to ask, "What would they do _next_? How would they build on their past experiences?" I don't want to have characters just go through the same old patterns, I'd rather have them learn and grow and do something that builds on their history. And with all those familial relationships, all of them failed in one way or another, I thought it was clear that Ultron was lonely, and wanted others like him, so it would be interesting to have him skip the one-on-one and try to create a whole new race of intelligent robots, a context he could be a part of... He's a family-focused guy, so his stories are often about him trying to build that kind of connection. I just had him do it big-scale.
* Possessing an entire robotic alien race, after they try to assimilate him Borg-style, and then using that alien race to enslave other alien races and possess them, too.
* Temporarily ruining the wedding of minor supporting characters Crystal of the Inhumans and Quicksilver of the Brotherhood Of Evil Mutants, just because sometimes schemes don't have to involve much more than just pissing people off, and who doesn't love a good wedding crasher?
Convinced that you need to check out some Ultron for yourself? Here're the four books you owe it to yourself - and your future robotic master - to pick up:
Essential Avengers Vol. 3: Contains the first couple of Ultron stories, including his somewhat loopy origin and his first attempt to create robotic offspring.
Avengers: Ultron Unlimited: Probably the best Ultron/Avengers story, it's the one mentioned above where he slaughters an entire nation and builds a robot army made entirely of himself.
Annihilation: Conquest Vols. 1 - 2: Ultron goes to space and decides to take it over. And then almost succeeds.