Answer: ANY
Effective leadership is not about personality style. It is about having a high degree of self awareness, putting you in a position of being able to augment your natural talents, counter your weaknesses and making choices about your own behaviours - at times, even going against your natural tendencies to achieve a certain goal. Effective leadership is a practice, not a personality type. The more one practices at being a leader, the better a leader you will be.
There are effective leaders of every personality type. People that fall into different personality styles all have potential to be great leaders, but their natural innate style of leadership will differ. Each personality type will have its own strength to bring to the table, and depending on the needs of an organisation, different leadership styles suit different environments.
The most common misunderstanding about personalities is the assumption that someone who is D (Dominant) style is naturally suitable as a leader. Yes, it is true that the D style leader tends to enjoy being in charge, and in fact they do also need to be in charge. But we should always bear in mind, that wanting to be a leader is not the same as being a good leader.
When in a leadership role, the D style leader is in their element. They get the opportunity to make decisions, to be actively involved by directing, assigning roles and providing direction. They are natural problem solvers and go getters. The D style leader may also be forceful, aggressive and task oriented - potentially causing some bruising of feelings and emotions along the way.
The I (Influencing) style leaders tend to be very relatable - the true people people. Their strength is in being able to influence those around them with their enthusiasm. They tend to be great at communication and are good with coming up with ideas, and are able to inject a fun element in getting a project going. These are the people who can move people along, by providing the "rah-rah". They love talking, and communicating, and are highly aware of the needs of the people in their team. However, follow through may not be their strongest suit.
You may have also met some leaders, who are a little quieter. Perhaps someone unassuming, who sits there quietly, but always attentive to everything that is happening around them. The S (Steady) style leaders, are not usually loud, but they are relational people, who are good at keeping the peace among team members. They are generally calm individuals, who favour peace and consistency. They place great importance on the overall well being of the group and not their own needs. They tend to be patient and provide a listening ear to those around them. Making decisions however may take a little longer as the S (Steady) style leader does not like conflict and prefers a decision that keeps the group happy.
The C (Compliant) style leader, is one who is great with details, analysis and structures. This individual may be particularly effective in industries which require a great deal of detailing work. The C style leader thrives in a situation requiring data and is very good at processes and complex information. They value accuracy, correctness, and have very high standards of work, and often expect the same high standard of others. The C style leader has a tendency to be very task focused and may favour getting the task done and lack sensitivity to people issues.
Most individuals however do not fall neatly into just one style. The large majority of people have blends of various styles, so for example, someone who is a SC (Steady + Compliant) style is able to lead the team by being both people centric, and relational while being able to have a keen oversight on data related problems. A leader who has no D (Dominant) style, but who is a SCI (Steady + Compliant + Influencing) style can bring all their strengths to the table and be able to be decisive, direct and behave just like a D (Dominant) style leader especially in smaller groups.
While DISC cannot be used to predict someone's leadership potential, we can however use DISC to develop leaders. An effective leader should always start with having great self awareness. Only when one has a keen sense of self awareness, can you then develop and practice the ability to adjust and adapt to people of different personalities. Developing people skills, which includes having the maturity and agility to communicate with all sorts of personality types, will mean that a leader is able to harness and augment the potential in the people around him/herself to the best of their ability, therefore bringing the team to a whole new level.
A leader who is strongly aware of the concept of DISC will therefore be able to understand people better, without being judgemental and always towards a positive focus. Leadership after all is about dealing with people who need to work together to achieve a common goal. Being able to motivate and encourage people with differing views and personalities can create a team that is highly effective, and highly creative as you put together the best of different worlds.