The Second Vatican Council says regarding The Pope and his power
‘But the college or body of bishops has no authority unless it is understood together with the Roman Pontiff, the successor of Peter as its head. The pope’s power of primacy over all, both pastors and faithful, remains whole and intact. In virtue of his office, that is as Vicar of Christ and pastor of the whole Church, the Roman Pontiff has full, supreme and universal power over the Church. And he is always free to exercise this power. The order of bishops, which succeeds to the college of apostles and gives this apostolic body continued existence, is also the subject of supreme and full power over the universal Church, provided we understand this body together with its head the Roman Pontiff and never without this head.(27) This power can be exercised only with the consent of the Roman Pontiff. For our Lord placed Simon alone as the rock and the bearer of the keys of the Church,(156) and made him shepherd of the whole flock;(157) it is evident, however, that the power of binding and loosing, which was given to Peter,(158) was granted also to the college of apostles, joined with their head.(159)(28) **’
And in a later clarifying note the same council says ‘. **The College, which does not exist without the head, is said “to exist also as the subject of supreme and full power in the universal Church.” This must be admitted of necessity so that the fullness of power belonging to the Roman Pontiff is not called into question. For the College, always and of necessity, includes its head, because in the college he preserves unhindered his function as Christ’s Vicar and as Pastor of the universal Church. In other words, it is not a distinction between the Roman Pontiff and the bishops taken collectively, but a distinction between the Roman Pontiff taken separately and the Roman Pontiff together with the bishops. Since the Supreme Pontiff is head of the College, he alone is able to perform certain actions which are not at all within the competence of the bishops, e.g., convoking the College and directing it, approving norms of action, etc. Cf. Modus 81. It is up to the judgment of the Supreme Pontiff, to whose care Christ’s whole flock has been entrusted, to determine, according to the needs of the Church as they change over the course of centuries, the way in which this care may best be exercised-whether in a personal or a collegial way. The Roman Pontiff, taking account of the Church’s welfare, proceeds according to his own discretion in arranging, promoting and approving the exercise of collegial activity.
**
4. As Supreme Pastor of the Church, the Supreme Pontiff can always exercise his power at will, as his very office demands.’
Moving onto sources that are not councils the most famous is probably the Papal Bull ‘Unam Sanctum’ which states ‘We venerate this Church as one, the Lord having said by the mouth of the prophet: “Deliver, O God, my soul from the sword and my only one from the hand of the dog.” [Ps 21:20] He has prayed for his soul, that is for himself, heart and body; and this body, that is to say, the Church, He has called one because of the unity of the Spouse, of the faith, of the sacraments, and of the charity of the Church. This is the tunic of the Lord, the seamless tunic, which was not rent but which was cast by lot [Jn 19:23- 24]. Therefore, of the one and only Church there is one body and one head, not two heads like a monster; that is, Christ and the Vicar of Christ, Peter and the successor of Peter, since the Lord speaking to Peter Himself said: “Feed my sheep” [Jn 21:17], meaning, my sheep in general, not these, nor those in particular, whence we understand that He entrusted all to him [Peter]. Therefore, if the Greeks or others should say that they are not confided to Peter and to his successors, they must confess not being the sheep of Christ, since Our Lord says in John "there is one sheepfold and one shepherd.’ and later most famously ‘Furthermore, we declare, we proclaim, we define that it is absolutely necessary for salvation that every human creature be subject to the Roman Pontiff.’