The Name Required for Salvation
Ahnsahnghong said, "Salvation is found in no other name than Jesus, not only at His first coming but even in the last days." (From The Mystery of God and the Spring of the Water of Life, page 181, Chapter 12, more here)
However, the WMSCOG says, "Today, salvation is only given through the name of Christ Ahnsahnghong." (From The Savior of Each Age and the New Name)
Whom Does Eve Represent?
Ahnsahnghong said, "Thus, Jesus is the last Adam, and the saints who are redeemed can be called the last Eve." (From Visitors from the Angelic World, page 55, Chapter 13, more here)
However, the WMSCOG says, "If Adam represents the Second Coming Jesus, whom does Eve, the wife of Adam, represent? Eve, called the 'mother of all the living' (Ge 3:20), represents our Heavenly Mother..." (From The Sabbath and God the Creator)
Keeping the Feasts of God
The WMSCOG says that the feasts of God must be kept correctly in order to achieve salvation. (From Salvation is Given to Those Who Celebrate the Feasts)
However, the WMSCOG does not keep the feasts of God correctly according to their own standards. (Click here for a detailed chart.)
How Many People Will Get the Seal of God?
Ahnsahnghong said that 144,000 is a literal number of those who have the seal of God, and only 144,000 will have the seal. He said, "some pastors or leaders of the churches that have a large congregation are trying to interpret it in a different way from the Bible because there is a big difference between the figure in the Bible and the number of their church members." (From The Mystery of God and the Spring of the Water of Life, page85, more here)
However, the WMSCOG registered one million members in April 2008 (source) and now says, "This [the seal of God] is a blessing given not only to the 144,000 but also to all who keep the new covenant. The Bible says that there is a great multitude that no one can count and that all people around the world will stream to Zion in order to learn the ways of God." (From Let's Become Worthy Believers)
The New Song Book
The WMSCOG says that the Pope is the Antichrist with the number 666 (Rev. 13:18) and that the Catholic Church is the great prostitute of Revelation 17. (source)
However, in their New Song hymnal is a Catholic hymn, "Faith of Our Fathers," written by a Catholic priest, F.W. Faber. (more here)
The WMSCOG says that Ahnsahnghong is the new name of Christ in this age. The age of the Son has passed, and you will not be saved if you cling to the old name of Jesus. You MUST use the name of Ahnsahnghong. (source)
However, on official documents filed with the Internal Revenue Service (IRS), they make no mention of Ahnsahnghong and only use the name Jesus, even when describing baptism. (more here)
The WMSCOG says that Ahnsahnghong was God the Holy Spirit in the flesh. In other words, they say Ahnsahnghong = the Holy Spirit = Jesus = God, all the same. (source)
However, Ahnsahnghong's tombstone says that he was "The Prophet Elijah." John the Baptist was also called an Elijah because he prepared the way for Jesus. Neither the Prophet Elijah nor John the Baptist were God. If Ahnsahnghong = Elijah, then Ahnsahnghong ≠ God. (more here)
This is a contradiction with history...
The WMSCOG teaches that the Antichrist (the beast with the number 666 from Revelation 13) is the Pope (the Papacy, the Roman Catholic Church). They say that the fall of the Roman Empire and the rise and reign of the Catholic Church fulfill prophecies about the Antichrist.
However, a study of history shows that their claims are false. They misrepresent the historical record in an attempt to force the prophecies to fit their theory. In particular, their claim about the 1260 year rule of the Catholic Church directly contradicts their own doctrine. (details here)
The WMSCOG says that "Mother Jerusalem" (Zahng Gil-Ja) has "loved us to the point of death" and "died in the place of sinners." (source)
However, Zahng Gil-Ja is still alive in Korea, and the WMSCOG teaches that she will not die at all, but take her faithful followers to heaven with her alive. (more here)
(I'll be adding more to this list in the future...)