There are several synonyms for the term "most mind altering" that can be used depending on the context. If the focus is on substances that alter the mind, some synonyms that come to mind include intoxicating, hallucinogenic, psychedelic, mind-bending, or mind-expanding. Alternatively, one could use terms like transformative, revolutionary, or life-changing to describe experiences that have a profound impact on one's thoughts, feelings, or perceptions. These synonyms may be especially appropriate when discussing spiritual or self-improvement practices, such as meditation, yoga, or therapy. Ultimately, the choice of synonym will depend on the specific meaning and nuances that the speaker or writer wishes to convey.