What is the difference between alcohol addiction and nicotine addiction?

Answer 1

For practical purposes none, except you are somewhat less likely to take other people with you if you just smoke.

The biggest difference is in the degree of lethality. Alcoholics who continue to drink will eventually die of alcohol-related causes. Smokers may not develop obvious smoking-related complications (although they are likely to do so), but it will inevitably reduce their quality of life, and on average will shorten it by about ten years.