After some thinking about why Ant-Man wasn't actually Avengers 2.3, I had an idea, what if Hank actually created Ultron? Scott didn't think he could handle it and just wanted to call The Avengers to handle Yellowjacket. But I got an idea, what if Hank Pym really did create Ultron? Why does Hank have such a deep hatred for the Stark family? Now I know what you're thinking, he just hates Tony because Howard stole his Particles from him without asking and was going to use them for his own needs. But no, This theory could blow that out of the water.
Why Would Pym need Ultron?
Now everyone knows that Pym created Ultron in the comics, but the MCU edition has Banner and Stark create him. But if Stark were to STEAL Ultron from Hank, then that's a pretty good reason to hate all but Maria Stark. But why would Hank even need Ultron? Because he needed a bodyguard. He wanted to build Ultron because he was ready to go mad with anger and confusion and grievance. With Janet's recent death, losing his daughter's trust, and the whole Howard ordeal, he wanted launch an attack on Stark Industries and he needed the protection from Stark, S.H.I.E.L.D, and even H.Y.D.R.A. But he realized the error in his ways and talked himself out of it. So he hid Ultron in an old Howard Stark warehouse that wasn't being used anymore so Hank knew he could hide it there. And then he hid himself away in an old mansion until Darren wanted to take over Pym Industries and Hank needed Scott.
How Did Tony Discover Ultron?
Well that's easy. He discovered him while cleaning out the New Avengers facility. And Stark was planning on just leaving the team before the events of AOU could even happen. But they found the H.Y.D.R.A base and some Ultron attempts that they stole but failed. So Stark took advantage of his circumstances and created Ultron. He used the blueprints he found in the warehouse with the failed attempts he found at the H.Y.D.R.A base to create a peacemaking super weapon of extinction. Just sayin'.