Without making me read a whole book to find the answer, what are some examples of cases where sanctions have worked?

It seems that sanctions are primarily useful at driving the target country into the arms of a larger adversarial state. And as a near-absolute rule, they never affect the leadership responsible for the behavior being sanctioned; only the common people suffer.

My impression is that economic sanctions amount to collective punishment, and are thus unethical. I still hold out hope that they will prove effective against certain egregious actors such as the Russian government, but I think it's fair to demand continuous oversight and adjustment to ensure the sanctions are having the intended effect, and not just causing needless suffering among people who are powerless to effect change.