unthinkable
adj.impossible to imagine or accept because it is so shocking or unlikely. You use this when something is too extreme to even consider.
adj.impossible to imagine or consider as a possibility; often used to describe events or ideas that are socially, morally, or practically unacceptable.
“A few years ago, a global lockdown seemed unthinkable.”
“The loss of the company's main server would have been unthinkable before they implemented the new backup system.”
“In the current political climate, a compromise that was once considered standard has become unthinkable to both parties, leading to a total stalemate in negotiations.”
Often used predicatively after linking verbs like 'be', 'seem', or 'become'.
“It seemed almost unthinkable that Pradhan, a core BJP leader who had played an important role in recent regional elections, would be compelled to go.”