Let me get this straight – there’s no real “antagonist” in Ratatouille like other movies until Ego.
You can’t really say Skinner is one because honestly, he’s just a good businessman.
Remy starts to grow an ego when Linguine starts to get attention for the food that he makes and that leads to him and the little chef having a fight down the line in Ratatouille.
Ego has this certain air about himself where he feels that whatever he says is gospel – which is overridden when he finds out that yes, Gustaeu’s does still make great food.