Having read some books about China, what strikes me is the vicious nature of torture often gets referred to. For example, Jung Chang claimed that some torturers would attach a wire to the penis and the ear and play it like an instrument. While this is purely my judgement, that kind of viciousness seems rare among torturers, largely because people will talk under less duress. I also vaguely recall sleep deprivation being invented in China, although that may be my memory playing tricks.
Anyway, I was curious as to whether some of the more shocking evidence was colonial propaganda, or China's large population gave birth to more sadists, or whether there is another historic root.
I think it's not that the Chinese have been exceptionally cruel with their punishments, it's that they continued with corporal punishment and torture after the west had (mostly) stopped the practice. Which was certainly a nice cudgel to beat them with in the 19th century. But if you look back a bit further, things were reversed.
In Gedenkwaerdig bedryf der Nederlandsche Oost-Indische maetschappye..., a 17th century book about the Dutch East India Company's activities in China, there is also a section with general information on China (from various sources). In that section (p.476) they mention that the Jesuit Nicolas Trigault though the Chinese punishments were weak. They 'only' used the death penalty for murderers and money forgers. (that page, and following, also has some etches of corporal punishment, mostly beatings, in China). When you look at what was going on in Europe at the time you can see where he's coming from.
EDIT: To give you an, extreme, example, in 1584 Willem van Oranje, leader of the Dutch revolt, was shot and killed. This is how they executed his killer, after severe torture.
his right hand was snipped of with red hot pliars
His flesh was cut to the bone with same pliars, in various places
He was quartered, alive.
His heart was torn out of chest and thrown in his face, though i imagine he was already quite dead by then.
he was decapitated for good measure.
EDIT2: All that said, i don't now how reliable the Jesuit's description is