What is the worst addiction you've ever quit?

The weed thread and people "quitting cold turkey" got me thinking,what is the absolute hardest addiction you've ever quit. And what were the worst withdrawals from?

For me the hardest thing ever that Ive quit was shooting heroin/fent. I've known plenty who didn't make it out alive and buried a really good buddy like two weeks before I went to Lincoln Nova over in Ruston to get cleaned up. First week in detox was hell, especially since I think I took my sub too soon and went into precipitated, but the other four weeks I was there was great and I really got a lot out of it. Way way way way better of a place than Fresh Start in Winsborro where I was dropped off a few months before that, I made it 3 days there.

The worst withdrawals I've ever had wasn't from heroin/fent, even the precipitated that I went in, but rather just lowly old Klonopins. I'm not really a fan of benzos but was prescribed them for a while for anxiety and panic attacks. Well because I'm me I abused them and after all my refills ran out I went into the worst withdrawals I've ever felt. Thought I was legitimately about to die.

Anyways I'm curious to hear y'all's take. I know alcohol can be really bad too and while I definitely am an alcoholic it never got to the point where I got the shakes or anything when I quit. And my DOC changed and just haven't felt the desire to have a drink since. Nobody I know that shoots up also drinks oddly enough. They'll do meth / coke / maybe smoke pot but generally not but none drink.