Assuming we're counting things that I've personally killed at least on a RTS squad level (none of the "I blew up a planet, and therefore billions" bullshit)....
Well, I'm pretty sure my kill count for Left 4 Dead 1&2+Team Fortress 2 add up to over 1,000,000 kills.
Then add all the Goombas, Koopa Troopas, robots, RTS units, other FPS/TPS troops, Pokemon, other zombies, random targets in Assassin's Creed games, RPG enemies, and aaaalllllllllll of the things I've butchered in Diablo games, etc etc etc etc....
I'm gonna have to say like 5,000,000-10,000,000 from everything ever combined, from the NES era til today.
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Yea, most of the people in the thread have no concept of realistic kill rates. 800 enemies per hour is like a constant infinite one-hit-kill swarm max for an FPS. That's like 4.5 kills per second.
To reach a "10 million in personal FPS kills"....that's over 600 hours (almost 26 days straight) of mowing down constant enemies that die to like one shot each.
Just 1 billion is virtually impossible, unless you're counting bullshit "mass" kills, like blowing up planets or something. In FPS terms, that's like 7 years, without pause for food or sleep, of killing stuff at full speed.