Yeah, but propelling them out of the solar system just sounds like the kind of fake-ending that ends up with the super villain coming back stronger in a decade. Have we learnt nothing from science fiction? You have to destroy your foes whilst you can.
7: When I've captured my adversary and he says, "Look, before you kill me, will you at least tell me what this is all about?" I'll say, "No." and shoot him. No, on second thought I'll shoot him then say "No."
13: All slain enemies will be cremated, or at least have several rounds of ammunition emptied into them, not Left for Dead at the bottom of the cliff. The announcement of their deaths, as well as any accompanying celebration, will be deferred until after the aforementioned disposal.
They can still come back from another parallel reality or some such - villains are like cats, they always come back (unless they are bored and then they don't).
But we gave him a nice little prison stay to write his manifesto in! Surely he learned his lesson and won't attempt to overthrow democracy again, right?