for me its galio, the only champ i havent lost in ranked with yet (that ive actually played with in ranked)

the 4 bans i see every game are amumu, shen, malphite, and rammus...being able to tank without using one of those changes the entire game (galio is probably the best initiator in the game...q/e flash/ulti and the entire team is at 1/2 health)

nothing turns a teamfight around like a 2 second taunt on the entire team with a nuke at the end

I agree with earlier post.

1vs1 a good tryndamere, and winning is impossible.

Boy this is a tricky question. 1v1 proabably jax or tryn like evryone says. With a well built taric, udyr or nasus you wont kill me 1v1. I may not kill you, but you will not be able to kill me even with ignite. I promise. Team fight changes everything. Champions like galio and rammus even amumu would get my vote. Vlad and mundo in 3's can do amazing. Depends i guess.

I don't know if I would say he is the best. However Olaf can be extremely powerful. That reason I go out and say this though is not only for being a good jungler, but his late game as well.

If Olaf ever gets a full build going, he is impossible to stop. Unlike Trynd or Yi or some of physical carry that can get rough late game. Olaf will begin to ignore pretty much all CC, while being extremely tanky, and worst of all for the opposing team? There is no mitigation for true damage.

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This being said. A well played Shaco will control the flow of an entire game. I personally think Shaco is the most powerful champion. However it is not because of his abilities. He pretty much scales purely on skill and game sense.

I know malphite isn't the best by far but he's my favorite and I love him so I gotta say anyone who knows how to build a decent malphite is gonna be hard to take down. Team fight I'd say galio. If you a galio manages to get even most of your team in range then you're toast if they have a single other powerful aoe spell on their team because you're now held in place while its beating on you. 1v1 I'd actually say it depends on who you're facing. An end game rammus vs a carry is going to win in a straight up fight nearly every time just because if he turns on that ball curl and his ult you're going to be doing next to nothing. regular I'm gonna go with tryndamere