I don't know which addictions are strongest, but I was addicted to both nicotine and alcohol at different times. Quitting nicotine was hard. Cravings persisted intensely for a year. Years later I broke the addiction cycle with alcohol. That seemed like a walk in the park compared to nicotine.
30 years ago, when I quit alcohol, I attended AA meetings where many members were sworn off alcohol, but unable to stop smoking. We had smoking meetings twice a week and we had big turnouts for those. The air was thick with smoke in those meetings, thicker I have ever experienced. OK I fought forest fires as a summer job. That may have been worse, but only sometimes.