Not by any stretch of the imagination
Definition 1 of 1
Pro Tip 1/3Strong Negation
Use it to express a very strong or emphatic denial about something's possibility or truth. 
He couldn't have solved that puzzle, not by any stretch of the imagination.
Pro Tip 2/3Idiomatic Context
Understand it's an idiom; knowing individual word meanings doesn't convey its full sense. 
That old car won’t win a race, not by any stretch of the imagination.
Pro Tip 3/3Emotional Emphasis
It often conveys the speaker's strong feelings or convictions about the statement. 
This isn't a good decision, not by any stretch of the imagination.