What can you say about the second coming of Jesus (I'sa) in Islam and Christianity?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Muslims believe that Isa will descend on earth before the Last Day.  He will kill the antichrist (Addajjal), break the cross, and rule according to the Islamic Shariah, the Shariah of Prophet Muhammad (Sallallahu Alaihi wa Sallam). 

There are evidences from the Qur'an as well as the Sunnah that prove his coming.  Allah Says (interpretation of meaning): {And he ['Iesa (Jesus), son of Maryam (Mary)] shall be a known sign for (the coming of) the Hour (Day of Resurrection) [i.e. 'Iesa's (Jesus) descent on the earth]….}[43:61].  Allah also Says (interpretation of meaning): {And there is none of the people of the Scripture (Jews and Christians), but must believe in him ['Iesa (Jesus), son of Maryam (Mary), as only a Messenger of Allâh and a human being], before his ['Iesa (Jesus) or a Jew's or a Christian's] death (at the time of the appearance of the angel of death)…..}[4:159]. In the Sunnah there are numerous Ahadith that prove this fact.

Al Bukhari and Muslim reported from Abu Hurairah that the Prophet (Sallallahu Alaihi wa Sallam) said: “By the One Whom my soul is in His Hand, Ibn Maryam (Jesus) will descend among you.  He will rule with justice and equity, will break up the cross, kill the pig and put Al Jizya…..”.  The Christians also believe that Prophet (Sallallahu Alaihi wa Sallam) Isa will come down to earth.  But their creed according to this issue differs from that of Muslims.  In fact, they believe wrongly that Jesus was killed before ascending to heaven.  As for us Muslims, we believe that Isa was not crucified and that he ascended alive and is still alive in the Heavens.  Allah protected him from the Jews and the Romans who plotted a filthy conspiracy to kill him.  But Allah made someone else resemble him.  So, they killed that man believing that they had killed Isa.

While the Christians believe that Jesus is the son of Allah the Muslims believe that he is a slave and a Prophet (Sallallahu Alaihi wa Sallam) of Allah.  Christians believe that Jesus will come down and raise the cross and that he will rule according to their laws and purify their faith in the Trinity.

Muslims, on the other hand, believe that he will rule according to Islam and that he will break the cross meaning his never being crucified will negate the belief in his crucifixion and resurrection.

To conclude, you should know dear brother/sister that this subject requires a much more detailed answer.  This could be found in books of Tafseer (interpretation of Qur'an) under the chapter that deals with the Signs of the Day of Judgement.