Green’s Dictionary of Slang

1. thuggish, pertaining to thuggery; usu. as king-hit merchant, one who specializes in thuggery.

1914		Sport (Adelaide) 14 Feb. 9/1: They Say [...] That Willie S. got his mouth knocked. behind his ear by the ‘King Hit’ mob, and he is still laid .
1944		L. Glassop We Were the Rats 76: ‘Do this galah over,’ he whispered in my ear. ‘He’s a king-hit merchant.’.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 33: King Hit Merchant Thug.

2. knocked out, struck down.

2004

T. Winton ‘Family’ in Turning (2005) 172: He’d left the TV on its back, wide-eyed and out of commission, like a kinghit wingman.