Green’s Dictionary of Slang

(orig. US) to act aggressively towards, to coerce or intimidate.

1982		L.A. Times 21 Nov. IA 6: Paul’s really hard-balling it now.... They’re locked in a relatively high level for competition [HDAS].
1989		Gorelick et al. Destruction of Evidence (1995) 69: Many judges are thought to be inured to the ‘footdragging, sandbagging, stonewalling, and hardballing’.