In terms of scaling with items, Taric.
In terms of team utility, Lulu.
In terms of offensive power, Leona.
In terms of defensive power, Janna.
In terms of anti-team utility, Alistar.
In terms of initiation, Sona.
Then there are some who can do numerous things like Soraka -> heal, global ult, disruption/sustain e, but no skill of hers is as broken as Thresh Q/W or Blitz Q. The latter 2 stay relevant through disruption and utility, but Alistar seems superior in that regard.
After all it's pretty hard to categorize since champion kits have different categories of skills. Would we have an Alistar with his e and r replaced with more disruption, he'd be the king of it, but botlane would be a lot more like pokemon.