What’s harmful is the inhalation of the thousands of chemicals into your lungs from a burning cigarette.

Nicotine could be considered bad because its addictive qualities make smoking happen more frequently, but rising blood pressure is a small piece.

Nicotine may be mildly harmful, but in a similar ambiguous you-win-some-you-lose-some way to caffeine: https://www.gwern.net/Nicotine

Nicotine isn't good for you by any means, but lung cancer is the main reason cigarettes are uniquely harmful. It's a really rough way to go.