Handbook of International Diplomacy―The Authoritarian Edition: THREATS 101
When issuing international threats forthrightness & scope of vision is essential to establish your credbility to your oppenent nations or entities. Lukewarm and insipid intimidations are interpreted as telltale signs of indecison, internal disagreement and, crucially, weakness. Bullying declarations should leave no room for being surpassed by more catastrophic counter-threats.
For example never threaten to bombard a specific city, do it for the whole country. If you are considering travel bans go the extra mile and apply them to the whole populace. Wording is of the outmost importance to get your message across loud and clear and to avoid misinterpretation. Sanctions should be "crippling" or "paralyzing", strikes should be "cataclysmic" or "apocalyptic", etc. Allusions to infamous euphemisms of the yonder past are always a plus. Take time to study the master of this art, North Korea, recently threatening its southern neighbor with "final destruction".