I feel like Carcel's infidelity at the beginning doesn't matter to me so much because Ines had no feelings for him in the first place. He did exactly what she expected him to do. I know a lot of people still hate him for that, but he's definitely making up for it imo.
It would be different if Ines desired his affection from the start, but she felt indifferent to him and we see now that her indifference made Carcel feel like like whatever he did didn't matter to her. Was it a childish/stupid way to get her attention? ofc, but Carcel's feelings towards Ines have always been childish and immature...but he only ever feels/acts this way around Ines (▰˘◡˘▰)