I've never ever seen that happen to anyone... If you try, you'll always get a D or a C. With a D you had a REALLY bad game.
I feel really bad too. http://media.tumblr.com/tumblr_ltjp3aYYZ51qaweyv.png
Don't you have to afk or feed intentionally for that?
Closest thing was me getting a D+ as Rumble because I didn't farm alot and was so outmatched that I ended up 1/7. If I'd went afk the rest of the game, then it would make sense.
wait there's grade F? what...I actually don't think I've ever gotten lower than a C- in LoL
There's an F grade? I personally haven't seen anything lower than a C...
What do I have to do to get an F grade? Take a step further than intentionally feeding and help the enemy team push lanes by blocking my own creeps?
I'd say invade your own jungle but that means you get farm...