Quick aside because I find doing this stuff fun, let's compare kill counts! Between Kroq-Gar and Poppa Maz, specifically. Kroq-Gar is a merciless killing machine whose first kill was probably on the same day he climbed out of his spawning pool. He's been at it ever since, ceaselessly patrolling and killing the enemies of the Old Ones. He doesn't kill something every single day, of course - there's the requisite travelling from battle to battle, the training days, time spent commanding armies, all that. But he's still really good; let's say he's killed ... 2,500 people (not counting animals and daemons, that'd be unfair) per year, on average, for all 8,000 years he's been alive. Simplifying the numbers because I don't feel like doing complex math. That totals out to roughly 20 million kills to his name over the years. Golly, that's a lot! But he did spend pretty much his whole life doing this, so it kinda makes sense that a super badass saurus would be able to accomplish something like this.
Mazdamundi, on the other hand, despite being far older, has spent comparatively little time killing people, or attempting to do so - perhaps a thousandth of his time if you were being really generous. So what's his killcount? To know this, we need to take a look at the population of the Karaz Ankor right around the time of the War of The Beard. Now, the most comprehensive population calcs for that time I've come across come from Imrix, who estimated at one point that Ulthuan and its colonies had something like 15 million total elves around the time of the war, down from 25 or so due to Malekith's fuckery. I'll say the dawi had about 25 million souls at the time since they hadn't had anything to trigger their decline yet, and say that 5 million of them died in the war, for an even 20 mil. Then the Time of Woes happened, which was a time of calamity so great that even the Dammaz Kron, the Great Book of Grudges, doesn't have anything written about it. It at the very least involved a great deal of earthquakes and volcanic eruptions that sundered their Underway across the scope of 2 continents, cut off all their holds from each other, collapsed a great deal of mines and caverns, and opened up the doorway for the orks, goblins, and skaven to commence their fuckery that then continued for the next several thousand years.
This was the result of Mazdamundi trying to correct for unwanted continental drift that had occurred since he'd last looked at the Old World.
Now, it's kind of hard to attribute all the deaths the Time of Woes caused to Maz, because then you'd have to account for pretty much every event in the Old World beyond it, so we'll just take the deaths caused directly by the earthquakes, as well as the immediate aftermath such as trapped dawi starving to death under piles of rubble and whatnot. Given that the dwarfs lost a good deal of their major holds in the decades afterwards, I'd say about a third of them died as the mostly-direct result of Mazdamundi's realignment effort. So that's about 6.6 million kills to Mazdamundi ... in a single ritual, by accident.
Now if we include all the species native to Mallus he helped exterminate with his terraforming way back when, he definitely beats Kroq-Gar's total, with a fraction of the time dedicated to actually killing people. I'm not including daemons because their numbers during the Catastrophe were limitless and casualties didn't always stick.
That's just canon stuff on Mallus, not counting the 300+ million orks he Ocean Man'd out of existence here.
