How will you best answer the question "What One Skill Does a Project Manager Need in order to Succeed?"

Apart from all basic qualities :Expert crisis management skills

"Communication skills"..

Communications is the key, more than70% of all tasks, coordination, expectations, and management tasks entails communication.

Even co-location may have communication barriers if not managed properly.

Knowledge in Domain Standard Business Process Experience & Change Management Skills .

Any implementation, change management is a big task for all PMs. To change the organization's  end user from their legacy system to the new ERP or any other application system, its not an easy job.  To handle the situation as in decent way, the PM should take responsible to conduct frequent awareness training program with awaited benefits presentation's of the new system comparing with the legacy one.50-70% of the projects are almost completed if the PMs keep this major area focus in his mind .

Also he should know fair knowledge about the particular domain standard business process to ensure the data flow and modules integrity.  This is almost solve all the client level queries & escalations.

Next, the PMs should have the capable of effective communication and presentation skills.

These are all the major points which will enable the PM to success any project within the timeline period.

He need to be a Leader with best communication skills

Project Managers skills are same as operations manager most of it in addition to it they need the below 

• Credibility – the project manager is coming into an established organization and must have a reputation or presence of credibility to receive the respect and support of the client and team.
• Creativity as a problem solver – projects are never “business as usual”.
• Tolerance for ambiguity – a project manager can often be unfamiliar with the kind of work the client does and needs to be able to adapt and move the project forward, even if all aspects of the company aren’t understood perfectly.
• Flexible management style – a project manager is constantly dealing with new people and environments and must adjust accordingly. They do not have the luxury of an established rapport with their project associates.
• Effective communicating – because of the ambiguous nature of projects, good communication skills are crucial in understanding what is expected by the client and being able to convey that vision to the project team.

As there is a difference between the two ops and project manager

• Operations managers are long-term focused and process oriented. Project managers are goal directed and milestone oriented.
• Project managers need the same skills as an operations manager, such as good communication, team building, planning, expediting, and political sensitivity.
• Project managers need additional skills in establishing credibility, creative problem solving, tolerance for ambiguity, flexible management, and very good people skills.

Analytical Skills: The ability to think through problems and decisions. The ability to serve, motivate and focus a group and to foster collaboration among team members

Communications

True leader with a good communications.

There is no One Skill / Mantra to be a successful Project Manager.

Essence of Project Management is PLAN WELL and EXECUTE WELL with an ability to adapt / mitigate as required.