When someone is on a mission to destroy something or someone, it is important to find the right words that accurately convey their intentions. Some synonyms for the phrase "be out to destroy" include "have a vendetta against," "take aim at," "set out to ruin," "seek to annihilate," "pursue a destructive goal," "plot against," and "work towards devastation." These phrases highlight the malicious intent behind someone's actions and the harm that they are capable of causing. It is important to recognize these warning signs and take action to prevent any destruction from occurring.