Another moment was in 'The Avengers' when they first teamed up. They were getting to know each other's fighting styles and personalities. This was the start of their friendship. They learned to complement each other in combat, which was crucial for the success of the Avengers' missions.
In 'Avengers: Endgame', when they were planning the time heist. Their shared determination to bring back everyone who was snapped was evident. They respected each other's opinions and skills during the planning process. Black Widow's sacrifice was also a significant moment related to their relationship as it deeply affected Captain America and the rest of the team.