My sister and I came up with the most insane theory. (Maybe not, but it's something to think about.)
So I wad reading this fanfic
(Awesome fanfic by the way, go read it.)
Anyway, I already had a theory that Ultron wasn't Tony and Bruce's doing, but this fanfic put my thoughts into words.
This is Loki talking to the Avengers of his mind control and it just made me think. If Thanos could put an "imprint" of his mind on Loki, he could do the same thing to the Mind Stone.
Sceptre:
Mind Stone:
What if the blue outer casing on the Mind Stone in Loki's Sceptre was an imprint of Thanos' mind. That would mean Ultron,
Who wanted to save the Earth by destroying the Earth, is a miniaturized version of Thanos,
Who wanted to save the Universe by destroying the Universe.
Thus, Ultron would now be Thanos' fault. Because Bruce and Tony weren't even close to an interface.
P.S.
I also blame this Bitch,
For mind raping a super-genius with PTSD. What the fuck was she expecting in return? Flowers?! Unicorns that eat Skittles and shit rainbows?!