There are two major problems here:
1) Did you acttually watch the same movie as everyone else?
Cross felt betrayed by a mentor who neglected and turned on him.
Kay.
Yeah, I heard the half-ass line meant to stand in for character development.
So...
-Why did his mentor neglect him?
-Why did his mentor abandon/turn on him?
-How did that actually affect Cross? Who was he before?
-What does it mean in relation to the movie's key themes?
The answer the movie gives us is:
"Because I saw too much of myself in you".
What the hell does that even mean in context?
Where in Hank Pym's characterization did we even see a HINT of the man Cross became?
The movie does NOTHING with this angle. Nothing. There is no exploration or resolution of their relationship and its conflicts. It's all vague "we had problems" nonsense. Soap operas have better writing.
He was slowly being driven crazy by his research.
Umm...when?
He was an arrogant, murderous ******* who was obsessed with his work, but "slowly driven crazy?" Yeah...no. He seemed fully aware of what he was doing and why.
Nevermind that this is, again, incredibly generic, and it was not handled with any interesting twist or exploration.
2) So basically what you're saying is everyone has to be a world-stopping powerhouse to be a threat? It's not just you, but leading up to Ant-man, people were constantly complaining about the "Marvel formula" and how they needed to do some smaller scale threats. Now they do, and those same people turn on them
for it.
No...I didn't say anything close to that. At all. Although let's not pretend that the movie didn't try to establish a larger threat here, with the sale of the weapons to Hydra having (vague) global implications. Nevermind that the thread Hydra poses is some vague "Oh no, Hydra will have the technology". That's supposed to be a threat with stakes?
And that's the problem. There were no stakes. The threats had no teeth.
I'm fine with a smaller scale threat. You want me to feel like his family and his daughter are in danger, fine. Here's a helpful hint. Don't skip to the daughter already being captured and have her actually, I don't know, be terrified about things. Have him destroy the house. Terrorize the family. SOMETHING. Maybe don't have the mother escape to call the police. Maybe have someone actually get hurt or face some kind of serious obstacle. Just spitballing some ideas here.
There's no tension-building moment where the villain attacks the home, terrorizes the family, nothing (which is also kind of generic, but at least it helps with tension building).
They're just like "Let's skip to there being a reason they have to fight".
And earlier, Scott doesn't ever appear to be in any real danger during the heist. At one point, Cross has him trapped in a little glass thing with a laser grid, and there's no "Ok, gonna zap him dead now" moment. Nope. He doesn't threaten to use the now captured Ant-Man in his scientific experiments down the line. To use the captured Ant-Man suit to unwrap more of Hank's secrets. He doesn't hold Hank's failure over his head. Just...nothing.
Heck, the only ones in any danger during the heist were those ants on the bottom of the floating ant thing. They're the greatest heroes of all.