Crocodiles are the largest predator of humans so its no wonder "Gustav" tops the list. I've also read Gustav's range is not just limited to Burundi but literally several hundreds of miles up and down the Nile river through several countries. Among his famous killings are a well-known priest and a famous reporter who was tracking him. Following maybe the largest mass killing of humans by any predator:
"..The most deaths in a single crocodile attack incident may have occurred during the Battle of Ramree Island, on February 19, 1945, in what is now Burma. Nine hundred soldiers of an Imperial Japanese Army unit, in an attempt to retreat from the Royal Navy and rejoin a larger battalion of the Japanese infantry, crossed through ten miles of mangrove swamps that contained saltwater crocodiles. Twenty Japanese soldiers were captured alive by the British, and almost five hundred are known to have escaped Ramree. Many of the remainder may have been eaten by the crocodiles, although since this incident took place during an active military conflict, it is impossible to know how many deaths can be directly attributed to the crocodiles instead of to combat-related causes. .."
Source:
http://en.wikipedia.org/wiki/Crocodile_attacks