Damn, I don't know that I've ever gotten a D. I think it's because I rarely play support, so my CS always makes up for the rest of my score in bad games. A bad game as support and there's nothing to fall back on.
My worst game in a while might have been 2 games ago. Played Fiora for effectively the first time vs Gnar, which isn't a bad matchup, but I just got camped to shit by Nunu without my jungler ever coming up. I barely missed out on First Blood because of an early gank, and then barely missed out on another kill. My lane snowballed completely out of control and the enemy team kept roaming on me, and I was like 1/9/1 at 20 minutes.
Then I 1v1d Draven and shut him down because Fiora is a broken POS in duels, and we still managed to eventually win.