What champions do you summoners think is a bit too OP? I would say Master Yi against new players, but once you know how to counter him with your specific or favorite character, he's not too bad to be faced against, but my actual choice would have to be Ashe, I understand that she is a carry, but she can easily get first kill, almost every match.
UPDATE : OP to me means Strong and Annoying (SA), but on another look through the champions after playing a few matches the other day, I would have to pick Hecarim as my choice. He has massive damage late game and he's hard to kill, because of his defense builds, the only thing I could really do to him was silence him when I was playing LeBlanc, our entire team was defeated by Hecarim.. It may be sad, but honestly, he was an honoured player, so that might have contributed to the fact that we lost that game.