That depends on what you mean. Tobacco - bad for lungs, throat, mouth. Alcohol - bad for pretty much all of you. Pot - bad for your brain, and other areas depending on how you take it. Can also trigger psychological disorders like schizophrenia.

I fear that legalization won’t come with the education that’s necessary to counteract the “marijuana is healthy” crowd that make that leap because you can’t die from it. It’s pretty clear it’s terrible for developing brains.

I have used all three, and cannabis is the least habit-forming, in my personal experience. Even if it was able to produce the same negative physical effects as tobacco or alcohol, that makes it less pernicious, imo.