A common technique for retrospectives is to invite Appreciations from the group, which provides an opportunity to acknowledge individual efforts have not gone unnoticed by their teammates. Appreciations are described by starting with the person's name followed by a short description of what they did which you appreciated. When inviting appreciations, I ask the team to write a post-it note for each team member and list one helpful/useful thing that you personally appreciated.

However, sometimes developers can find it uncomfortable to work in postive-mode as they normally prefer problem solving. I think it makes Appreciations easier when you couple them with surfacing some Commiserations. Where a commiseration is "one thing that a person in the team did that you wish could be avoided". 

Inviting the team to call out commiserations is a practical way to connect heroic efforts with areas for potential improvements. You can then use the commiserations as a stepping stone into identfying areas to discuss how they might be avoided in future.