Obadiah Stane was never on Stark's level. He was more cunning and could take tech from other people.
Stane isn't really as much of a tech guru as he is a financial and political person.
It's not that. Stane is great for most of the movie.
Until the end.
Then he sees Pepper walking out of his office, sees the computer open to all his crazy-ass jigs, and instead of, I dunno, calling security to rightfully detain her, he decides to let her go and dress up in a giant robot suit and murder her face.
I just can't wrap my mind around why anyone would think that's a good idea. Like, what was his game plan afterwards?
"Hey Obadiah, why you murdering your secretary there with a giant robot?"
"Oh... um... I... she broke the non disclosure agreement?"
"Uh huh."
It makes no sense that a cunning businessman like Stane would fuck up so badly. Even if he succeeded killing Pepper, he just totally fucked himself over, because killing someone with a giant robot that only one person has is not the sort of thing that will go unnoticed. And at some point, he's going to have to leave the giant robot, even if it's just to go to the bathroom, and he'll get arrested the moment he does so. It's dumb.
Whereas in the comics, you have a Stane who played the long game and just let Tony destroy himself before coming in and picking up the pieces. Totally legal slightly hostile takeover, but he had the law on his side. He was a smart businessman, not an engineer, but he still got the job done. Movie Stane just totally went insane at the end.
I get it, and I won't pretend I don't love the Trevor character, but Killian was a really lame villain to fall back on. The twist was a funny, unexpected moment but it also sucked all the tension out of the rest of the film.
I'll agree I was kinda "meh" on Killian, but the guy was kinda bonkers by that point on account as evidenced by the effect Extremis has on people, so I guess it could make sense that he was just saying crazy crap. Or rather, I should hope that Extremis has a mental component because otherwise, it doesn't make sense why all these soldiers suddenly go murder crazy when they're on it.