A did a small grep-n-parse to my logs that go back a few years,
and sorted the deadliest mobs (that shout when somebody dies).
This is how many times somebody has died to a certain mob.
(this is taken mostly from 08:00 EET to 23:00 EET)

3731 Guard
2579 Tythus
1340 Torturer
1149 Baal-Naygash
1025 Skeleton
889 Mortis
843 Troll
842 Demon
610 Great lion
530 Chaos Spawn
468 Raven Guard
463 Black pudding
454 Barbarian
445 Sable Bladetree
405 Cavalier
354 Yaboz
354 Black Reaver
345 Wainamoinen
245 Chimera
230 Oogga
217 Zyll
210 Despana
174 Lion
166 Magician of good
161 Arska
158 Strangler vine
156 Carnivorous plant
140 Dogface the troll
139 Kizarwexius
138 Tazla
125 Raztax
124 Jason Vorhees
118 Young seamonster
112 Black belt ninja
106 Pit fiend
105 Female Duz
94 Black Knight
92 Black bishop
91 White belt ninja
88 Akira
...
2 Half-dead pigeon

~/A

Ahah, proof positive that highbies are a bunch of weaklings. I always
suspected that black puddings were more dangerous than black reavers (or
Sable, the big girl's blouse).