Cautionary (adjective)

1. Serving as a warning or reminder of a potential danger, problem, or error.
2. Providing a warning or advice against something.

Origin:

From latin cautionem (nominative cautio) "a taking care, a taking heed".

Examples:

1. He gave a cautionary tale about the perils of drug use.
2. The story serves as a cautionary tale about the dangers of greed.
3. The article offers a cautionary note on the use of certain chemicals in food.
4. The story is a cautionary reminder of the dangers of neglecting safety procedures.
5. He is a cautionary example of how not to manage a business.