What qualities are essential for successful leadership?

A big heart and a big vision is the key to being a successful leader.  There are several parameters like communications, integrity, innovations, inquisitiveness, taking care of the team, accountability, resilience, accountability and ownership are a few qualities among a lot of other qualities.  Leadership comes naturally, experience and training make leaders more perfect day by day. 

I'd say the first quality good leaders have is vision, able to "see the big picture". Also, having the ability to convey that vision to others, and get them excited about it and wanting to be part of it. 
They should be able to think critically about the company or their team they work within, and then develop a clear understanding of its strengths, weaknesses, opportunities, and threats. They must be able to communicate with other people in a way that feels truthful and genuine. They must also be self-aware enough to understand their teams strengths and flaws, as well as be open to new ideas and perspectives that may mean a change of course, thus being adaptable when the situation calls for it. Ultimately, a leader needs to take responsibility for their, and their teams actions. Finally, A good leader knows how to take the long view, whether it's with strategy, a particular situation, or a goal.

1) Being vulnerable and Authentic 
2) Be empathetic 
3) Lead by Example -  not ask the team to do more than what the leader is willing to do
4) Servant Leadership Mindset  

Passion, Compassion, Ownership, Reason, Vision and Above All, Honesty and Integrity.

Successful leaders are self-made. If you see yourself as a leader, that essence will be evident in your work, because leadership is more about who you are than what you do. But it is a journey; nobody can become a leader in three to five years. And the more initiative you take towards becoming a leader, the closer you’ll get to becoming one.

You need to be very good at communication, which is not only about speaking, but listening as well. Only once you listen properly will you be able to decide your next course of action. Many people emphasize speaking when it comes to communication, but listening is more important. Successful leaders also leave their ego at the door. You encounter many situations when you are working in an organization where people may say something to you that you don’t agree with, but you don't have to react immediately. You need to leave your ego behind in those moments. 

A leader should also have a vision for whatever they are doing, including values, goals, a mission, purpose, and clarity. You need foresight to anticipate what might happen. And successful leadership requires courage because you need the ability to both take on risk and manage a crisis. Leaders should never stay in their comfort zones. If you are staying at one company or in one role because you’re comfortable, you won’t keep developing your leadership skills. The more challenges and responsibilities you take on, the better a leader you become. Leaders hold themselves responsible and refuse to make excuses if something goes wrong. They stay calm and focus on doing better in the future. And they are also great readers. When you read books relevant to your role or domain, you get so many ideas. Leaders always need new ideas to implement the right strategies, so I read two to three books per month.

Integrity is a critical quality and one of the most important leadership traits because it guarantees all the others. Leaders need to demonstrate truthfulness and consistency: How truthful are you with yourself and your team? And how consistent are you in fulfilling promises made to your shareholders, organization, CEO or team? How are you fulfilling those promises? But most of all, leaders have to be very good at creating cooperation between departments.