Who is an Antichrist?

He is the enemy of Christ , and it is believed that He will reign dreadfully before the  Last Judgement.
He will appear to deceive humanity before the second coming of Jesus .
In John it is mentioned 5 times about the Antichrist.
Bible doesn't tell us who is the Antichrist , But speaks to us about the traits He will possess.
 
References: 

Revelation 13:1-10

The Beast out of the Sea

13 The dragon stood on the shore of the sea. And I saw a beast coming out of the sea. It had ten horns and seven heads, with ten crowns on its horns, and on each head a blasphemous name. 2 The beast I saw resembled a leopard, but had feet like those of a bear and a mouth like that of a lion. The dragon gave the beast his power and his throne and great authority. 3 One of the heads of the beast seemed to have had a fatal wound, but the fatal wound had been healed. The whole world was filled with wonder and followed the beast. 4 People worshipped the dragon because he had given authority to the beast, and they also worshipped the beast and asked, “Who is like the beast? Who can wage war against it?”

5 The beast was given a mouth to utter proud words and blasphemies and to exercise its authority for forty-two months. 6 It opened its mouth to blaspheme God, and to slander his name and his dwelling place and those who live in heaven. 7 It was given power to wage war against God’s holy people and to conquer them. And it was given authority over every tribe, people, language and nation. 8 All inhabitants of the earth will worship the beast—all whose names have not been written in the Lamb’s book of life, the Lamb who was slain from the creation of the world.[b]

9 Whoever has ears, let them hear.

"If anyone is to go into captive, into captive they will go. if anyone is to be killed with the sword with the sword they will be killed."

10

This calls for patient endurance and faithfulness on the part of God’s people.

Daniel 9:24-27

24 “Seventy ‘sevens’[a] are decreed for your people and your holy city to finish[b]transgression, to put an end to sin, to atone for wickedness, to bring in everlasting righteousness, to seal up vision and prophecy and to anoint the Most Holy Place.[c]

25 “Know and understand this: From the time the word goes out to restore and rebuild Jerusalem until the Anointed One,[d] the ruler, comes, there will be seven ‘sevens,’ and sixty-two ‘sevens.’ It will be rebuilt with streets and a trench, but in times of trouble. 26 After the sixty-two ‘sevens,’ the Anointed One will be put to death and will have nothing.[e] The people of the ruler who will come will destroy the city and the sanctuary. The end will come like a flood:War will continue until the end, and desolations have been decreed. 27 He will confirm a covenant with many for one ‘seven.’[f] In the middle of the ‘seven’[g]he will put an end to sacrifice and offering. And at the temple[h] he will set up an abomination that causes desolation, until the end that is decreed is poured out on him.[i]”[j]

2 Thessalonians 2:1-12

2 Concerning the coming of our Lord Jesus Christ and our being gathered to him, we ask you, brothers and sisters, 2 not to become easily unsettled or alarmed by the teaching allegedly from us—whether by a prophecy or by word of mouth or by letter—asserting that the day of the Lord has already come.3 Don’t let anyone deceive you in any way, for that day will not come until the rebellion occurs and the man of lawlessness[a] is revealed, the man doomed to destruction. 4 He will oppose and will exalt himself over everything that is called God or is worshiped, so that he sets himself up in God’s temple, proclaiming himself to be God.

5 Don’t you remember that when I was with you I used to tell you these things?6 And now you know what is holding him back, so that he may be revealed at the proper time. 7 For the secret power of lawlessness is already at work; but the one who now holds it back will continue to do so till he is taken out of the way. 8 And then the lawless one will be revealed, whom the Lord Jesus will overthrow with the breath of his mouth and destroy by the splendor of his coming. 9 The coming of the lawless one will be in accordance with how Satanworks. He will use all sorts of displays of power through signs and wonders that serve the lie, 10 and all the ways that wickedness deceives those who are perishing. They perish because they refused to love the truth and so be saved.11 For this reason God sends them a powerful delusion so that they will believe the lie 12 and so that all will be condemned who have not believed the truth but have delighted in wickedness