Choose clarity that fits the relationship
For a close friend, say that you are stepping away and give the main truthful reason at a useful level. For a casual connection, reduced contact may be enough unless they ask directly.
Avoid putting their whole character on trial
Describe the pattern or mismatch that informs your choice without collecting every grievance. A friendship ending is a boundary, not a verdict others must enforce.
Close shared responsibilities safely
Return belongings, settle money, leave group roles, and agree how mutual events will work. If there is intimidation, stalking, or abuse, block and use trusted, specialist, or legal support.