Exceptionally strong willed people, yes might be able to break the curse. The few examples we saw of a struggle, Pious and Bode were both ministry workers.
Common public would probably be completely blameless in falling under it. Since it isn't a spell someone prepares to experience 24/7. Which makes it such a good defense for death eaters. They cursed me in the back while I was walking down the street. They imperiused me in the middle of a heated battle to protect my family! Imperiused people don't act like dummies, they're capable of normal conversations and such like Pius proved in deathly hallows. So you can't say something like they didn't act like a imperiused victim.
Since Harry, himself took several times while being prepared before he could throw it off himself and in the graveyard Voldemort, made him bow before he could throw off the curse. It's hard, even when you are prepared.
Why not? We've never heard of a magical limit outside of fanon? A wizard has never been seen running out of magic or anything like that.
Common public would probably be completely blameless in falling under it. Since it isn't a spell someone prepares to experience 24/7. Which makes it such a good defense for death eaters. They cursed me in the back while I was walking down the street. They imperiused me in the middle of a heated battle to protect my family! Imperiused people don't act like dummies, they're capable of normal conversations and such like Pius proved in deathly hallows. So you can't say something like they didn't act like a imperiused victim.
Since Harry, himself took several times while being prepared before he could throw it off himself and in the graveyard Voldemort, made him bow before he could throw off the curse. It's hard, even when you are prepared.
(*) I mean, did they even explain who was CASTING all those Imperius Curses, if all of them were supposedly victims of? Voldemort's good, but him and Bellatrix ain't holding down 20+ Imperius Curses each all by themselves. Their stories were patently unworkable.