the odds of a successful assassination are sufficiently low that the net effect of trying to change things with an assassination attempt is close to zero.
If I may say so, those odds seem a lot better than the usual options like 'write letters to the newspaper' or 'start a political party'.
On the other hand, the risks and costs of the letter are much lower than an assassination. The monetary costs of starting a political party are probably comparable or higher, but the personal risks are probably lower unless you're in a country where ending autocracy is a really good idea.
Is working within an existing party just too disgusting to think of?
Risking your life to get less war probably makes sense on utilitarian grounds unless the war is likely to get rid of a very bad government.
A reminder for everyone: on this day in 1983, Stanislav Petrov saved the world.
It occurs to me this time around that there's an interesting relationship here - 9/26 is forgotten, while 9/11 is remembered. Do something charitable, and not patriotic, sometime today.