"Tone down" is a common phrase used to describe the act of reducing the intensity of something. There are many synonyms that can be used to express the same idea. Some of the most commonly used synonyms include "soften," "diminish," "lessen," "moderate," "mellow," "temper," "subdue," "restrain," and "calm down." Each of these words conveys a similar meaning to "tone down" and can be used interchangeably depending on the context and desired effect. Whether trying to convey a less aggressive tone or simply scale back the intensity of a situation, using one of these synonyms can help communicate the desired message.