Episcopal ordination - fullness of the sacrament of Holy Orders
The Second Vatican Council "teaches . . . That the fullness of the sacrament of Holy Orders is conferred by episcopal consecration, that fullness namely which, both in the liturgical tradition of the Church and the language of the Fathers of the Church, is called the high priesthood, the acme (summa) of the sacred ministry."
Source: Catechism of the Catholic Church (Vatican.va)