Has to be crack. When you struggle to get one last good hit from the residue, after all the money is gone, it's 3 in the morning, you have to work the next day, these things add to the tremendous amount of depression you are feeling naturally from the comedown, maybe this is the trade-off for coke not being physically addictive. Like others said you feel very very low, still want more, and God help you if you don't have a nicotene, a couple beers, some weed, a xanax and a couple lortabs, or at least a couple from this list. You will truly be in for a rough ride, with a monster on your back. Those were some of the lowest moments of my life, as a naturally happy-go-lucky type, I had some insight into what true debilitating depression might feel like. Though I must say, after a heavy night of smoking crack, a couple beers, a couple hydrocodones, and some weed made for an actually amazingly strong buzz, very pleasant and erasing the comedown quite completely.
I would imagine meth to be in the same ballpark.
Alcohol sucks when it is on it's way out. At least you can sleep the comedown off, but anyone who has drank too much too late and has to wake up too soon will know what I mean when I say that the alcohol comedown is one of the worst scatterbrained shit feeling comedowns you can feel.