Alternative Character Interpretation: Is Thor really a loving father who just wanted to teach his daughter a lesson in humility and had no option but to return to rule Asgard after Odin's death, or a cowardly slacker dead beat dad with insanity issues and a possibly cruel sense of humor?
Complete Monster: Ultron, built by Tony Stark to assist The Avengers and bring order to the world, decided the best way to bring order was to be the one giving orders. This drives him to betray and murder most of The Avengers, with Iron Man barely escaping with The Avenger's children in tow. After 12 years, during which time Ultron conquered half of the planet, killing millions and driving the survivors underground, he locates Iron Man hiding out in a base in the Arctic. Smashing his way in, he confronts the children, now teenagers, and attempts to kill them for being "potential threats." The kids escape while Ultron beats down Iron Man, at which point he captures and proceeds to torture him for information regarding the kids. When the teens sneak into Ultron's HQ to rescue Tony, they stumble upon Ultron's Trophy Room, showcasing the hundreds of signature items of superheroes he murdered over the years. The children later try to use The Hulk, who had been hiding out in the desert over the years, to destroy Ultron; however the machine bests him and then prepares to kill the children for possessing the "superhuman variable." While both Ultron and Stark would claim he is a creature of logic, Ultron shows through his megalomaniacal and cruel personality that this is just a poorly-veiled attempt to differentiate himself from the humans he so despises, and yet resembles in more ways than he'd ever admit.
Unintentionally Unsympathetic: The film explains that Thor left Torunn on Earth so she would learn the same lesson he did, but it completely ignores that Thor only needed to learn it that way because his own father failed to instill it while he was growing up and went for the tough love approach to get it through. Thor makes no attempt to teach her at all and just figures she'll learn it on her own, which makes him come off as an amazingly lazy father. After all, it's not like Odin didn't have the time to raise Thor, and surely Thor could at least try given he has some understanding of where Odin's parenting style was lacking.
James Rogers. He ends up activating the Iron Avengers and giving away their location to Ultron all based on the (not quite plausible) possibility that the robots had been programmed with the exact memories and personalities of the original Avengers, hoping that at least this was the case for his dad's robot.
All the kid heroes have moments of this. Which makes some sense because they're, you know, kids.