Nicotine can KILL. I am a health specialist, and while it is hard to "overdose" it can happen, especially with the liquids for vapes; but it depends on body size, health conditions, method of delivery, etc. Smaller adults, and especially children and pets are much more susceptible to poisoning via accidental ingestion. The "other stuff" in tobacco is commonly present in just about all botanicals when burned; just in higher or lower concentrations. Smoking cannibis presents a similar situation except for the addictive nicotine is not present, jury is still out on how addictive cannabis is considering the increased THC levels existing in the cannibis commonly found nowadays which is "not your Dad's weed" from yesteryear.

We use poison every day in healthcare, but a poison given in the correct doses to create the desired result is often lifesaving; it's called medicine at that point. Go out and pick some foxglove flowers, poisonous; but when used for certain heart conditions, the digitalis can save your life. There are many examples of this in the medical field.

By the way, my personal irritant is the term "medical marijuana". We don't call morphine "medical heroin", but essentially it is. Chemicals within the cannabis plant should be broken down and called what they are. People seem to love their CBD, but many don't know what it means or what it is; just that it comes from "POT", but I'm all for alleviating pain and discomfort so use what works for you.
Jumping off my "low horse" now, but I could go on ad nauseam.