Top Ten Heresies

Doctrinal or Moral Error	Refutation
"God is something that only pertains to religion."	False! The existence of God can be proven scientifically [Denzinger #4206]
"Jesus was a great man, an extraordinary prophet."	False! Jesus is all that (he is really a man), but Jesus is also Almighty God [CCC, #464].
"The Church is an invention of men."	False! The Catholic Church was founded by Jesus, and transmits through its official teachings all of the saving doctrine of Christ [CCC, #811, etc.].
"All you need to be a Catholic is to be baptized."	False! To be a Catholic, you not only need to be baptized, but you must also believe all the teachings of the Church.
"If you obey your conscience, you act well."	False! If our conscience is mistaken, we act badly.
"Mortal sin doesn't exist anymore."	False! A sin can either wound our soul (venial sin), or kill the life of God's grace in it (mortal sin).
"God is infinitely good. Everybody goes to Heaven."	False! The souls of those who died in a state of mortal sin go immediately into Hell. [Denzinger, #1002].
"It's OK to live together without being married, and to take the pill."	False! Fornication is severely contrary to the dignity of persons and human sexuality [CCC, #2353]. The use of contraceptive methods is a serious sin [CCC, #2370].
"Divorce is sometimes acceptable."	False! Christian marriage is endowed with the greatest indissolubility, and no human authority can touch it [Denzinger, #3712].
"The Eucharist is only bread."	False! After the consecration, it's Jesus Christ, really and substantially present. [Denzinger, #2535].
"Abortion is sometimes acceptable."	False! Direct abortion, either as an end or a means, is always an abominable crime.
"A good Catholic can reject the Vatican II Council and the CCC."	False! One must grant a religious submission of our intelligence and will to a doctrine of faith or morals asserted by the Pope, even if he doesn't have the intention of proclaiming it with a decisive act. [Code of Canon Law, #752].

Notes:

1) God is Love, and the Catholic religion only exists to bring men to let themselves be loved by God. The Church doesn't condemn heresies because She is nasty, or because She doesn't have anything else to do, but She condemns them to protect people against what can cut them off from God's love.

2) This is a chart showing doctrinal and moral errors that are prevalent in Quebec these days. It is not a religion course! If you know nothing about the Catholic religion, don't start here! Start with the Gospels and the Catechism.

3) Currently, I don't have access to scientific polls to support the listing and ranking of a heresy in this Top Ten Chart. I'm doing my best with the information I have.