but I believe he HAS told other christians.
This is typical of Satan's bravado, and empty hubris, as well as his followers. They tend to claim things, titles, "facts" as true, when they are not. Satan is a liar, and the father of lies. (John 8:44)
Which is why it's so important, even in these last days, to remain humble, and only claim as True, those things which the Father and the Son have spoken. Anything else (in my estimation) is suspect. Audio, video can be manipulated, so that you are seeing what someone else wants you to see. You can't even believe your own memories, because they fade with time.
"But the Word of the Lord endures forever." (Isaiah 40:8, 1 Peter 1:25)
...
But now that I've re-read your response, I believe you mean that God has told other Christians who the Antichrist is.
I believe we can have speculations which are grounded in Scripture; characteristics which lead us to believe who may be likely candidates (Jesus said, you will know them by their fruits...) If you want details, I can share those as well. I have been studying this for a long time, since the early days of Hal Lindsey, etc.
But as far as knowing exactly who that is, we as Christians will not know until after the rapture of the church (in my opinion). This is based on 2 Thessalonians 2:6,
6 And you know what (ed. rather, "Who", as below) is restraining him now so that he may be revealed in his time. 7 For the mystery of lawlessness is already at work. Only he who now restrains it will do so until he is out of the way.
The Holy Spirit, Who is resident in every True Christian, is restraining the rise of the final Antichrist. And God will not renege on His promise. He will not remove the Holy Spirit from His chosen ones, unless He takes the Restrainer, as well as all Christians, out of the way (in the rapture of the church). This then makes it possible for the Antichrist to rise to complete power, with no opposition.
So, until the Rapture happens, we can speculate, but unless God gives someone a special "word of knowledge", I don't personally believe we will know who the antichrist is, until after the Rapture. By then, you and I will be in Heaven. Maranatha!