Breathing, even though breathing is extremely dangerous. Evidence shows that 100% of all people who breathe will die. This can be traced back genetically; everyone who breathes was born to people who had also breathed during their lifetimes.
I hear folks that drink dihydrogen monoxide can become addicted after their first sip. One sip, and they are chasing that dragon for the rest of their days on earth, sad really. It's why I only drink soda, love me some sugary teeth rot