Kontra
It depends on what, who, and why you want to annihilate. The purpose of your "annihilation" will determine if you are good. Or evil. If you want to annihilate something for your own benefit only, consider yourself as evil. But, if your goal is to annihilate something that causes the real destruction, you are in the good side.
Like what the Voidians are doing, We are exterminating the pests of this universe. To make everyhing better. But as to why we only accept offers from the evil hearted beings, we won't reveal anything.