实锤 + perfective 了 — 'solid proof has landed'. Used for gossip scandals (affairs, plagiarism, cheating) when screenshots or video surface. 了 marks the moment the truth gets nailed down.
culture
Born on Chinese entertainment Weibo around 2014 (CC-CEDICT dates 实锤 to that year). The image is a blacksmith's hammer (锤) striking something solid (实) — you've pounded the case shut. Twitter equivalent: 'got the receipts'.
