Grasping the nettle

Read in the Daily Express (no snide comments, please!) appalling article about Stalin's "Poison Dwarf", Nikolai Yezhov, who was responsible for the deaths of some 3 million people, most of them innocent.

I suppose it's a dangerous question to ask, but is assassination always morally wrong? Was the life of Nikolai Yezhov really worth the lives of 3 million of his victims?

This article justifies it in the context of Israeli national self-defence (no spittle-flecked anti-Semitic comments, please, the same arguments can be expressed using other contexts), but what if the enemy is within one's own society? For example, was Stauffenberg correct in his attempt to blow up Hitler, his leader?

I suppose this must lead to the question of whether right and wrong actions receive their due in another world, rather than this one, where villains appear much safer, live much longer, than the innocent. Mao, Stalin, Pol Pot, Idi Amin...