[Seiryuu]

Originally Posted by prenet

how about naruto, he has evil thing inside him

Yes he does, but his goal is to either keep it sealed or control it somehow and take its power from it so that it can't cause harm. I'm looking for something where the ultimate evil is lying dormant, possibly without any real sign that it will awaken soon, and someone specifically tries to awaken it and break its seal out of some sort of necessity.

One example scenario, though I don't know that I've seen something like it before, would be

Spoiler for a speculative idea:

Two beings are sealed, one a dark "lord" and the other a near-omnipotent beast that (s)he controls. It is inevitable that the lord will awaken some day, and this awakening will free the beast from its chains. If the lord has the beast, no one will be able to stand against them. Thus the only way to stand a chance is to forcibly call forth the beast first, and attempt to destroy it so that the lord will have to fight alone. This is just a vague speculation as to a scenario where summoning such a demon may be truly necessary, and I don't know that I've seen it before.