James Vaughn has a blog on a research looking into characterises of the worlds best coaches. 

In summary: Read a lot, know thyself, and know your athletes.

Some key highlights below: 

the study was commissioned to better understand “serial winners”. Fourteen coaches from multiple fields – team and individual sports based around the world – where chosen for their abilities to develop Olympians and title winning dynasties.
This search – according to the data – is driven by a deep dark doubt, driving the obsession to ‘stay ahead’. These coaches are “always striving, driven by the fear of not being good enough”
These elite high performance coaches are visionary leaders, described within the data as ‘benevolent dictators’ – they are future orientated with excellent communication up and down the line: they have the capacity to simplify complexity when they communicate to their athletes. This is not disregarding complexity; they embrace and understand it, but are able to communicate in simple terms.
Most have also undergone a shift in leadership styles, moving towards a leader-follower approach, in which care and empathy are critically important.
these coaches know themselves – they know their core values and what it means to embody them, or how to demonstrate those values to themselves and their athletes.
‘what would have improved their coaching the most’, a theme emerged from all the coaches interviewed: “they said they wished they knew the athletes better”
Source: https://playerdevelopmentproject.com/key-c...
AuthorJoel Filliol