Stupid. Stupid, stupid, stupid. They should never have made a general intelligence, not without massively more testing. Just because aliens who evolved on other planets ended up with bizzarely humanlike minds and priorities doesn't mean something that was programmed instead of evolved would be the same. He and Tony rushed to get it done before the inevitable next alien invasion (and, might as well be honest with himself, before cooler heads stopped them) and now instead of all getting killed by aliens they're all going to get killed by his own creation, which is so much lamer, not that it matters because they'll all be dead.
Unless, that is, he can figure out what the thing in Loki's scepter did to their code, and stop Ultron first. He has it hooked up to a dozen different instruments, monitoring its every twitch--and then suddenly they all go crazy at once, and something scarily reminiscent of the portal over New York appears on the other side of his workbench.