It may seem red card is undeserved but there is rule that says when you defend by touching the players face with your hands you will get a straight red. If he touches his chest then he will get a yellow, why use hands? he might have stopped him without hands also. This generally happens in every match but we don't see red cards in every match, it is kind of debatable.
Anyway bad defending from Chiellini in both cases, but ronaldo over reacted as always and they say that only neymar does play acting. However we can also take this from different perspective like ronaldo intentionally moving alongside chiellini and letting his arm near his face and then start over reacting. That will be just disgraceful, and very bad for a player like ronaldo.