Hypnosis offers no risk or danger. Hypnotists are a different matter.
As with any profession Hypnosis has had it’s collection of charlatans, con-men and rogues, as well as a few incompetents to boot.
Fortunately the misuse of hypnosis is limited to a few cases where the hypnotist has misused suggestions to get their own way. In reality using just hypnosis to get what you want from someone is unlikely to work since the client is fully aware of what is going on, however hypnosis and hypnotic language along with other tricks and skills can be used when trying to con people.
Incompetence is a different matter entirely and there have been several cases of hypnotists or hypnotherapists causing distress to a subject through badly worded suggestions. Often this can be easily rectified with the help of a competent hypnotist.