A few things that wont break champions viability that need to be done...
If Syndra dies her ult needs to stop Take away Yasuos shield or make him earn it somehow Tryndamere needs to have his ult timer reduced drastically and/or the cooldown increased Make Veigars cage CD longer or make it not last as long Teemo's shrooms need to have their life span cut to about 25% Make Vaynes condemn a skillshot Take away Garens silence, he is too tanky for that Fizz's ult needs to have a smaller hitbox Shaco should just go invisible like wukong, He shouldn't be able to jump across a lane with it Annies passive needs a second timer or should require a fifth ability. Ryze's W needs to be a skillshot Kennens stun w/ passive needs a cooldown Camilles jump across the map ability needs to not also be a stun