I shudder to think
From Longman Dictionary of Contemporary EnglishI shudder to thinkI shudder to thinkspokenBAD used to say that you do not want to think about something because it is too unpleasant I shudder to think what they’ll say when they see the mess the house is in. → shudderExamples from the CorpusI shudder to think• I never know how carefully. I shudder to think.• Palestrina! I shudder to think what I should do when her next social invitation arrives in the letter box!• I regularly see them sent out alone on shopping errands. I shudder to think what might happen on their way home.• I shudder to think what will happen to him now.