well I simply played through l4d on normal, which was a challenge for me to say the least. I just assumed my level was low.
admittedly I couldn't clear the last stage because AI is garbage and I'm not even 100% sure I'm supposed to jump into the horde to go reactivate that generator that always deactivates no matter how fast I boot all three
gave up on that pretty quick because I saw no value in trying.
got a little into l4d2, but my progress is negligible. I did get to the part where you just carry a whole pile of gallons next to a fancy car and then shove them down all at once because you're lazy to fight six hordes