Tā shū le zhīhòu kāishǐ làipí, bù chéngrèn jiéguǒ.
After losing, he started acting like a sore loser and refused to accept the result.
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赖皮 is colloquial and mildly derogatory. It describes someone who avoids responsibility, reneges on agreements, or acts in a shameless, childishly stubborn way. Less severe than 无耻.