Fetching details from the dictionary...
difficult to imagine; quite unlikely to; very doubtful; would not expect
そのような事態は考え難い状況だ。
Such a situation is hard to imagine.
三十年前にこの技術の発展は考え難かった。
Thirty years ago, this level of technological advancement was hard to imagine.
そのような失敗が起きるとは考え難く、皆が驚いた。
It was hard to imagine such a failure happening, and everyone was surprised.