The moment his interests were harmed, he immediately showed his vicious side.
Tips
usage
毕 here means 'fully / completely' (as in 毕业 'finish studies', 毕生 'whole life'). The image: a previously hidden ferocious face now totally on display. Strongly negative — used when someone drops a polite mask and reveals genuine cruelty.
register
Common in news writing, fiction, and dramatic spoken Chinese. Compare with 原形毕露 (yuánxíng bìlù, 'true form fully revealed'), which is broader — any hidden nature exposed; 凶相毕露 specifically frames it as ferocious/menacing.
