The murder of that Iranian general may not ignite a war but I can’t imagine any kind of good outcome from this. And by the way, there is no such thing as a “preemptive attack”. An act of war is an act of war.
I’ve often wondered why the Germans didn’t launch large scale commando raids against the USA in retaliation for our bombing of Germany. The Germans had the commandos and the submarines to bring them here? The Germans could have done a lot of damage and caused a large number of civilian causalities until caught.
The Germans did attempt a number of those raids, all failed. One of the best documented is this one.