Imaam Muslim reports in his compilation, the Sahih, from Hishaam bin Aamir al-Ansaari, that the Messenger of Allaah (alayhis salaam) said:

There is not between the creation of Aadam until the (last) Hour is established a tribulation greater than the tribulation of the Dajjaal (Anti-Christ).

When this is the case, then a) there was no Prophet sent by Allaah except that he warned against the Dajjaal (Anti-Christ), and b) the Prophet Muhammad (alayhis salaam) stressed emphatically upon the Ummah (Muslim nation) to seek refuge in Allaah from the Dajjaal. These two affairs will be documented separately.

This tribulation will be greatest for people who are accustomed to ignorance of the foundations of their religion, who routinely fall into sin, disobedience, following or indulging in lusts and the likes of music which is a tool of "intoxication" and "beguilement" through which people are led into the corruption of their attitudes, beliefs and ideas, and through which people are verily easily led and directed. And Allaah will grant the Dajjaal powers and abilities by which he will deceive the people, as occurs in other texts that we shall document. Thus we learn that Dajjaal will have many means at his disposal. And so it is upon the Muslim to consolidate his faith and to keep away from those things that will make him susceptible to being misguided and led astray.