Direct threats require decisive action. Dick Cheney
Don’t make a threat and then not do it. Suzanne Vega
I consider it a mark of great prudence in a man to abstain from threats or any contemptuous expressions, for neither of these weaken the enemy, but threats make him more cautious, and the other excites his hatred, and a desire to revenge himself. Niccolo Machiavelli
Threats don’t work with the person who’s got nothing to lose. Maduro Ash
A piece of advice always contains an implicit threat, just as a threat always contains an implicit piece of advice. Jose Bergamin