A good Scrum Master needs to have these top soft skills to be effective in their role. The list is by no means comprehensive, please feel free to add more in the comments.
Communicator – the primary function is communication and the use of communication to get things done. The Scrum Master is always facilitating meetings and driving an agenda. Without solid communication skills this is difficult.
Listener – Scrum Masters need to master the ability to listen at level one and two. Not only do they need to follow what is going on in the project and control boundaries of work to be done, they also need to listen for impediments.
Persistent – the Scrum Master is the process gatekeeper. We all know that most people is anti change, so the Scrum Master’s persistent behavior in getting people to collaborate is crucial.
Facilitation – a good Scrum Master must have mastered the art of facilitation. It’s definitely a vital component in the overall success of yourself as well as your teams. Keeping meetings on track, documented and ensuring outcome calls for good facilitation.
Accountability – a Scrum Master is ultimately accountable for the delivery process, so the person should know the dynamics around RACI associated per role. This role ensures that others take responsibility and steps in to action this when required.
Servant Leader – the Scrum Master (and any leader in an agile organization) is a servant leader by nature and natures this quality in others on the team.
Negotiator – this role will constantly be interacting with the product owner and the team, and needs to shield the team from taking on too much work, and similarly shield the product owner from under-commitment in the Sprint. All this takes great negotiation skill.
Knows how to handle conflict – in this role there will be times when you are expected to step into the heat of the moment and get everyone back to their adult states. Knowing to not take sides and to neutralize the situation is key.
Motivational – Team motivational tactics is a key tool in the process facilitator’s tool-box. Most days some team or person requires just that bit extra attention and nurturing. You need to know how to pick up and action these queues.