You Can't Make Changes Without Embracing Change
You have boxed yourself in. The very fact that you're asking this question is in indication that there is friction between this developer and the team's chosen process, although you haven't actually defined the nature of the problem this is creating.
You're also looking to resolve this friction without requiring that the developer adapt to a team-oriented process, and are therefore willing to break the process rather than acknowledge that this team member may not fit within it. You simply cannot maintain the status quo and resolve this friction simultaneously.
You have essentially made the Scrum framework optional for this developer, but are trying to have your cake and eat it too. If you are going to allow each individual on the team to pick and choose the parts of the framework they like and are willing to follow, then you are not just inviting Scrum-Buts but essentially abandoning the rigor (and most likely the benefits) of your Scrum implementation.
It's okay to say that a given framework doesn't work for your team and your organization; there are certainly other frameworks to choose from. However, you must have some project management framework with rigorously-enforced controls in place if you don't want to invite anarchy.
Prima Donnas Aren't Agile
You have someone who isn't fitting into your team-oriented process. That leaves you with the following options:
- Re-evaluating the format and effectiveness of your retrospectives, and then tweak the ceremony until it's providing value to everyone.
- Providing education, incentives, and consequences to ensure that all team members participate effectively in this mandatory Scrum ceremony.
- Ditching the Scrum process if you aren't planning to follow it anyway.
Scrum is about teamwork. Lone wolves, even if they are technical rock-stars, are toxic to agile processes.
Retrospectives are Required by the Scrum Framework
One of team members says that he doesn't benefit from retrospectives.
This team member is missing the point. Whether or not he benefits from the retrospective is irrelevant; the real issue is whether or not the team benefits from the retrospectives.
In addition, the Sprint Retrospective is a formally-defined Scrum ceremony that is essential to the inspect-and-adapt process. That means that you must hold retrospectives if you're adhering to the formal Scrum framework. Failing to hold effective Sprint Retrospectives reduces the effectiveness of the framework, and is counter to core agile principles.
Finally, you must carefully consider whether you are willing to have your process hijacked by someone who is unwilling to be a fully-functioning member of the team within a team-oriented agile framework like Scrum. If you allow this team member to dictate process to the rest of the team, or to unilaterally pick and choose the elements of the Scrum framework that he wishes to follow, then this is neither agile nor Scrum.
As the Scrum Master, if you abdicate your responsibility to referee the Scrum process in order to placate an individual, you have failed to do your job. Instead, you should ensure that the retrospectives provide value to the team, and that the team functions as a team at all times.