to the core
From Longman Dictionary of Contemporary Englishto the coreto the coreCOMPLETELYextremely or completelyshaken/shocked/thrilled to the core When I heard the news, I was shaken to the core. That woman is rotten to the core! He was a bureaucrat to the core. → coreExamples from the Corpusrotten to the core• The financial system is rotten to the core.• Her very moral fiber was rotten to the core.