Tā zuìzhōng zài yālì xià xiànxíng, bàolù le zìjǐ de běnláimiànmù.
He finally showed his true nature under pressure, exposing his real face.
Tips
usage
现形 often carries a supernatural or figurative flavor - a disguised creature or person being exposed. 露出原形 is a close synonym also meaning to reveal one's true form.
