expression, noun-modifying (irregular)
Literally 'with rotten guts'; a strong, figurative expression describing a person whose character is fundamentally corrupt or morally decayed. Used prenominally to modify nouns like 人間 (person) or 政治家 (politician).
彼は腸の腐った政治家だ。
He is a corrupt politician.
あの腸の腐った人間には関わりたくない。
I don't want to have anything to do with that depraved person.
A fixed expression composed of 腸 (はらわた, 'guts') + の (possessive particle) + 腐った (くさった, past form of 腐る, 'to rot'). The image of rotting entrails metaphorically represents a thoroughly corrupt inner nature.