Who is the best scaling legit (not ap mageish) support

I'd say Alistar scales the best for the tanks, just because his CC is infinitely more useful in teamfights than Leo's. Braum's ult is fine, but that's all he has to be useful with mid game.

Taric scales the best for tank supports, as he scales on multiple forms of defensive stats, health and armor, while also hard scaling on CDR because of his passive.

Thresh might be a good contender because of his soul collecting passive

Leona, lol. There's nothing scary about Leona in the lategame. In fact, she falls off harder than most supports do.

IMO tie between Taric and Alistar. In terms of scaling.

Taric has a hard time in the early game. But he can become quite the beast late game with items.

Alistar is up there because of his powerful CC and ult.

So I should buy alistar?

Depends what you mean by scaling.. In terms of viability through out the game and being strong. Thresh hands down. 1. Tanky 2.lots of CC 3. get out of jail free lanturn

Alistar. Percent damage reduction scales incredibly well.