In Scrum, the accountability for creating a valuable and useful Increment every Sprint lies with the entire Scrum Team. Apart from this, each role has their own distinct responsibilities as well.
The Product Owner who is the face of the customer is responsible for maximizing the product's value and acts as the connect to the stakeholders. He prioritize and manage the Product Backlog, and decides on what should be included in the Increment to ensure it has a value. He also decides the time to market for a product and also the needed MVP (Minimum Viable Product), hence we call him the value maximizer.The Scrum Master plays a vital role in the Scrum framework, with responsibilities that include facilitating Scrum events, coaching and mentoring the team, removing impediments, fostering collaboration, protecting the team from distractions, monitoring progress and reporting to stakeholders, and promoting a culture of continuous improvement. As a servant-leader (true-leader), the Scrum Master ensures the Scrum Team understands and adheres to Scrum principles, while guiding and supporting them to achieve their goals and enhance their effectiveness through the use of Scrum practices.
The Development Team, consisting of self-organizing and cross-functional professionals, takes on the task of actually creating the Increment. They possess the necessary skills to deliver a potentially releasable product Increment. While the team members may differ in their specializations, they collaborate closely with the Product Owner to understand requirements and transform them into a shippable Increment.
Throughout the Sprint, the Development Team manages their own work, deciding how to best achieve the Sprint Goal and deliver value. It's crucial to note that each Increment created within a Sprint should be potentially releasable, meaning it should be in a state where it could be released to users or customers if the decision is made to do so.
To summarize, the entire Scrum Team shares accountability for the valuable Increment, with the Product Owner prioritizing and managing the Product Backlog, while the Development Team takes on the responsibility of creating a usable Increment each Sprint.