This seems to be rather random thoughts that don't appear to be supported by anything in particular.
The Three Calamities seems to be a rather popular topic, but I get the impression people are easily swayed to think that the other two are people who ate a mythical zoan DF or some other kind of a super beast DF. The reality is however that Jack's title and his DF have little in common and that his DF animal on itself isn't that particularly impressive. Agreed a mammoth is huge, but compared to something like a Hydra or Chimera, it's really just a fluffy elephant. A mammoth also has nothing to do with droughts. The reason why he was given that title, was because he had such a savage personality. He was such a savage he would destroy villages and towns to the point they're beyond restoration.
Now it's safe to assume that they will have Zoan powers with the whole animal theme. On top of that the term "calamity" is mostly associated with natural disasters and a drought is a prime example of such a disaster. Droughts lead to starvation which leads to death. So in my opinion the last two calamities will have titles that also refer to such disasters. This is also compatible with the animal theme of Kaidou's crew: animals and natural disasters. Things like "the damned" or "the despair" sound ominous, but as a calamity it's hollow and shapeless. It doesn't mean or points towards anything. You just used words that sound scary, but have no meaning. If I would make a guess, I would say that one of them will be called "the Plague" or something along those lines. One of biggest, and by many considered the biggest, calamity humanity ever faced, was the Black Plague during the 15th century. The culprits? Rats. So I'm going to drop the idea that one of the calamities at the rat DF or another DF of animal that's closely related to plagues, like locusts. Yes far less impressive than a Hydra or Chimera, but I think that line of thought is closer to the truth than just making a list of all the most powerful animals humanity ever imagined.