"Titsonabull" burns through all 13 of Left 4 Dead 2's campaigns on "Expert Realism" difficulty without the aid of bots.
Some people can play the entirety of Super Mario 3 without having Mario stop moving. Some people can clear Half-Life 2 in in under 90 minutes. Some people can build computers in Minecraft. Left 4 Dead 2 expert "Titsonabull" can finish the game's entire campaign mode on its hardest difficulty setting without the aid of any bots.
As if you didn't already feel bad enough about your stupid friends not being able to cover your ass while you try to fill up the car with gas in Dead Center, this guy does it all by himself. The two-and-a-half minute highlight reel shows how Titsonabull gets out of some of his hairiest situations, including being cornered by swarms of infected, "tounged" by smokers and pounced on by hunters. His weapon of choice appears to be the automatic shotgun.
It should be noted that "Realism" mode is an extra difficulty modifier that sits on top of the usual Expert difficulty. In Realism, only headshots will kill zombies, the Witch will instantly kill anyone who she hits, and the glowing outlines around weapons and special infected are removed. Expert difficulty basically buffs all of the regular and special infected, while making medkits and other items spawn at a much rarer rate.
If you're interested in seeing how he completes each level, you can check out the full playlist of his playthrough on his youtube channel, and ask yourself what the most impressive thing you've accomplished this week was (mine was cooking dinner).