From Longman Dictionary of Contemporary Englishguilty/shy/mad/angry etc as hellguilty/shy/mad/angry etc as hellspoken not politeVERY very guilty, shy etc If I had your problems, I’d be mad as hell. → hell
Examples from the Corpus
guilty/shy/mad/angry etc as hell• Strong, dedicated, skilful, passionate, intelligent and as angry as hell.• Whenever her family had been mentioned she looked as guilty as hell.• I was as angry as hell.• The Jaguar is reported to have crashed in a distant country, mad as hell.• She washed spiders down the plughole, and felt guilty as hell about it.• Lucy was shy as hell, and Jay was sure and easy.• These people were mad as hell. 