No, opiate withdrawal can also sometimes be fatal for a variety of reasons, but it is very uncommon, and withdrawal from some benzodiazepines can trigger seizures that have a small chance of a fatal outcome.
Yet alcohol withdrawal without medical supervision and possibly medication is by far the most dangerous, and probably has caused more fatalities than all other withdrawals combined.
This coming from me that is a recovering alcoholic that has had two withdrawal seizures, or "rum fits", and it is especially these than can easily trigger a stroke or heart attack. I was just very lucky to be hospitalized for the first one, and given Valium, while the second one was a lot milder, and just temporarily paralyzed my legs.