In my mind the apocalypse will probably come as an Ice age, here in my version, a fallen angel of death has decided to bring down the apocalypse without God's permission.
Her Mentors voice rang strongly in her ears as she performed her frozen duty. "An angel of death does not show mercy. An angel of death does not forgive. An angel of death does not accept repentance. However, Most of all an Angel of death does not pass judgment, for this is not the angel's job. Reap all the souls to heaven so that they might be judged before the highest."