Originally Posted by Hyde
He's not the most likely candidate because the entire point of Ultron is that he's created with good intentions but turns evil which makes the audience sympathize strongly with the hero who created him, not the villain who created him.
Why are you assuming that, when it's never been stated in any of the interviews with Joss or Feige, and when that was never the case in the comics....?
Nobody in fandom ever "sympathized" with Hank Pym about his creation getting out of hand, or even considers him some great hero and role model. He's still universally loathed as "that crazy wifebeater guy," no matter how unfairly.
And since the movies obviously aren't going the Hank Pym route anyway, then it's completely up in the air as to whether a good guy creates Ultron with good intentions, or a bad guy creates Ultron with bad intentions, or any combination thereof.