heavy blow; major blow; severe damage
Used for a serious setback, shock, or damage, often in emotional, financial, or reputational contexts. Can be literal (physical strike) but more often figurative.
そのニュースは彼にとって大打撃だった。
The news was a heavy blow to him.
The company suffered a major blow due to the recession.
Compound of 大 (だい, 'big, great') + 打撃 (だげき, 'blow, strike, damage').