Don’t queer the mark with warnings.
If you need to do something, just do it. Quietly, efficiently, don’t take credit, don’t let anyone know.
Some organizations are rich and powerful enough that they can make credible threats without reprucussions. When the US military or police kill someone, they make sure everyone knows about it. Sometimes they splatter the corpse all over the TV, as they did with Osama, Saddam and Qaddafi.
And the public cheers. As I have written many times, the American public loves torture, arson, murder and robbery – as long as a uniform does it. WN is not like the USG. We have no money and few men.
Leaving a calling-card, in any form, makes investigative aspects easier. No one investigates the USG when it murders. You cannot compare those working with and without government approval.
It is always easier to work a soft target than a hard one. Always. Make things easy on yourself and strive to make the job easier.