So Jesus called them and said to them, “You know that among the Gentiles those whom they recognize as their rulers lord it over them, and their great ones are tyrants over them. But it is not so among you; but whoever wishes to become great among you must be your servant, and whoever wishes to be first among you must be slave of all. For the Son of Man came not to be served but to serve, and to give his life a ransom for many.”
(Mark 10:42–45, NRSV)
As far as I’m concerned, this is the beginning, end, and totality of leadership training needed in the church. Anything else is abuse of leadership.