crack detective; tough detective; relentless detective
A detective known for being exceptionally tough, relentless, or uncompromising, often with a nuance of being feared by criminals and sometimes by colleagues. The 鬼 (oni) prefix adds a sense of demon-like intensity.
He is so relentless in cornering criminals that they call him a demon detective.
Cases handled by that crack detective are always solved.
Compound of 鬼 (oni, 'demon') and 刑事 (keiji, 'detective'). The 鬼 prefix is used figuratively to indicate a person of exceptional intensity, toughness, or relentlessness in their role.