I think all of the following - which are viewed to be heretical by the Orthodox Church - occurred prior to and were either confirmed or passively reconfirmed (i.e. not renounced) by Vatican I:
1. Rejection of original text of the Nicene-Constantinopolitan Symbol of Faith (Creed), as ratified by the Church at the 2nd Ecumenical Council in 381
2. The doctrine that the Pope can teach any dogma on his own authority, without the consensus of the Church; to whit (#3 and #4):
3. The doctrine of the Immaculate Conception declared by Pope Pius IX in 1854 (a declaration that Vatican I affirmed to be ex cathedra after the fact) that there was God intervened extraordinarily in Her conception.
4. The doctrine of the Assumption affirmed ex cathedra by Pope Pius XII in 1950 that the Virgin was assumed bodily into heaven without dying
5. The doctrine of a state or condition of purgatory after death where sinners pay off the temporal punishment that they allegedly owe to God for their sins, and the accompanying doctrine surrounding indulgences
6. The doctrine that Christ's crucifixion was a payment of a debt of punishment that humans owe God for their sins and not, rather, "that Christ’s self-offering to his Father was the saving, atoning, and redeeming payment of the debt of perfect love, perfect righteous, obedience, gratitude, and glory that human beings owe to God."
7. The doctrine that the Pope can teach any dogma on his own authority, without the consensus of the Church.
8. The doctrine that the primacy of the Pope includes ecclesiastical authority over bishops under the authority of other Patriarchs or over his fellow Patriarchs themselves other than that as the chief spokesperson for all bishops in apostolic succession.
I don't think I put what I felt about Vatican II correctly. Actually, I think Vatican II did take the Roman Catholic Church in the right direction in some respects (e.g. a clearer acceptance of conducting the Liturgy in local languages). After considering your question, I realize I did not think very clearly on this.
My comments about Vatican II came from personal feelings rather than clear thinking. Perhaps Vatican II was only coincidental and not the root cause of many of the changes I saw growing up as a Roman Catholic, but it seemed to me that following Vatican II, the Roman Catholic Church tried to make itself seem "more Protestant", for whatever reason. In 1978, I was a student at a high school run by Benedictine monks, who would serve a 7 am Mass every day with Gregorian chants. Although my local parish did not have these kind of masses, it still retailed the same sort of piety. The last time I visited a Roman Catholic Church (2011), it was for the funeral of someone who was being cremated, in a large "megachurch" style brick building with no statues or images of any kind and not even a cross. Except for a tablecloth and chalice on the altar and the priests vestments, one would have thought one was in an auditorium.