Many critics are bothered by statements from early LDS leaders on Joseph Smith's role in the final judgement, including the following from Brigham Young:
Joseph Smith holds the keys of this last dispensation, and is now engaged behind the vail in the great work of the last days...no man or woman in this dispensation will ever enter into the celestial kingdom of God without the consent of Joseph Smith.... I will now tell you something that ought to comfort every man and woman on the face of the earth. Joseph Smith, junior, will again be on this earth dictating plans and calling forth his brethren to be baptized for the very characters who wish this was not so, in order to bring them into a kingdom to enjoy...he will never cease his operations, under the directions of the Son of God, until the last ones of the children of men are saved that can be, from Adam till now.... It is his mission to see that all the children of men in this last dispensation are saved, that can be, through the redemption (Journal of Discourses 7:289)
This issue has been dealt with rather cogently by many LDS apologists (see this page, for example).
LDS apologists have often appealed to texts such as Matt 19:28 and its parallel in Luke 22:30, where Jesus promises the twelve a role in the eschatological judgement of the twelve tribes of Israel, similar to the role some early LDS leaders expected the Prophet Joseph Smith to play:
And Jesus and unto them, Verily I say unto you, That ye which have followed me, in the regeneration when the Son of man shall sit in the throne of his glory, ye also shall sit upon twelve thrones, judging the twelve tribes of Israel. (Matt 19:28)
Methodist New Testament scholar, James D.G. Dunn, commenting on this text, wrote the following which I think LDS readers will greatly appreciate:
The exalted Jesus [promises the disciples a] sharing in divine functions, particularly that of judge: 'God will judge the world in righteousness by a man whom he has appointed . . .' (Acts 17.31; similar Rom. 2.16); 'We must all appear before the judgement seat of Christ” (II Cor. 5.10). But here again the most striking parallel feature of the then current Enoch speculation is precisely the role attributed to Enoch in the final judgement . . .Enoch is linked with Elijah in this role in 1 Enoch 90.31 and the Apocalypse of Elijah 24.11-15. In 11 QMelchizedek, Melchizedek is depicted as a heavenly being—apparently the angelic leader ('elohim') of the holy ones who execute judgement on Belial and his host (lines 13-14). In the Testament of Abraham 11 and 13 Adam and Abel are shown in similarly exalted roles. Perhaps above all we need to recall that in our own texts first the twelve are said to be given share in the final judgement (Matthew 19.28/Luke 22.30—sitting on the twelve thrones judging the twelve tribes of Israel), and then the saints as a whole--'Do you not know that the saints will judge the world? . . .Do you know that we are to judge angels?' (I Cor. 6.2-3). (James D.G. Dunn, The Partings of the Ways Between Christianity and Judaism and their Significance for the Character of Christianity [2d ed.; London: SCM Press, 2006], 246).