Provisionals (and series)
Anyone ever notice that as you win more and more games (I was 6/0 before I finally lost one), it's not the caliber of your opponents that goes up, but the skill level of your teammates goes down? It's not like, "Hey, test your skills against challenging opponents!" It's, "Hey, test your patience and ability to deal with the same baddie duo two games in a row!"
I also now know that Riot really does pick certain accounts to trash, because on my other account I can't win a game if my life depends on it, no matter how well I do; on top of which THAT account frequently disconnects in loading screen, while this one hasn't in the 8 games i played on it today.