Nature the beast means the inherent wildness or ferocity of a creature. There are several synonyms that can substitute this expression in appropriate contexts. For instance, "savage nature" can replace "nature the beast" to describe the inherent brutality of an animal. Similarly, the term "wildness" can work as a synonym for "nature the beast," emphasizing the untamed or uncontrolled behavior of a creature. Additionally, "instinctual impulse," "animalistic instinct," or "primal urge" are some other phrases that can effectively convey the meaning of this expression. Overall, these synonyms can help to portray the raw and untamed aspects of a creature's behavior and attitude.