A notorious monster is a phrase commonly used to describe a creature that is widely known, usually for being fearsome or difficult to defeat. However, there are several synonyms that can be used in place of this phrase. Some examples include legendary beast, infamous creature, monstrous villain, notorious fiend, or dreaded monster. Each of these terms carries its own connotations and can help to create a more vivid image in the reader's mind. Whether you are writing a horror story, a fantasy epic, or a video game guide, there is sure to be a synonym that perfectly captures the essence of your dangerous and intimidating creature.