1990osu said:

General Grievous

Nearly any possible potential fear of Grievous is eliminated as soon as he doubles over to begin hacking and wheezing...

Interesting point about that: in the original clone wars cartoon, the mini series one, the end of the series showed Grevious kidnapping Palpatine and it led directly to the beginning of ROTS. In the cartoon one of the Jedi (Mace? Yoda? I can't remember) uses the force to crush Grevious's midsection. I always felt like that was why he was hacking. Otherwise it seems pretty random.