Ironheart
In 2024
You're probably meaning Indefinite Armour buff?
Because the last champion with indefinite Armour was Arnim Zola.
Remember, buffs can be Nullified or Punished - in fact they're more often a weakness than a strength. Aside from fighting a few Mutants, like Havok, they're less helpful than you might think. Arnim is massively armoured; it's just not Armour that can be easily removed by a Mystic or Cosmic opponent.
Bastion also has a armor I bet most of you don't know, and it allows him to parry non contact specials and heal damage when his block is broken. It is annoying to use him as an attacket this meta since one of the debuffs from node is armor break, which removes his armor and its ebenfits temporarily. I struggle to use him effieiciently against target matchups like zola and onslaught.