No, this is not a contradiction to say that only 1 & 2 John mentions the specific word "antichrist / s", with Christ using another comparable term for these which was "false christs" for the same type of persons.
That is not where the contradiction lies.
Scripture has Christ linking together as contemporaries the "false prophets" along with the "false christs" in Matthew 24:24.
Yep. That point is not in dispute. What is in dispute is the premise false Christs were limited to the brief period of time during and soon following John's epistles. They were not. They had existed prior to the Mount of Olives discourse. Their prior existence gave meaning to the words. The disciples understood the reference because there'd been many Moons and Koreshes throughout history. There was going to be an abundance of them in the last hour and one in particular - one among many - was of particular concern. John explicitly stated, "
even now many antichrists have come."
Many had come.
One was coming. Many had come.
Scripture has John also linking together in those first-century days the existence of "false prophets" as well as "antichrists" in 1 John 2 & 4.
The correlation between false prophets and messiahs is not in dispute.
And John also identified the Revelation 13 Land Beast as "the False Prophet".
Prophets are not messiahs or saviors. I might just as easily argue the beast is NOT an antichrist because he is called a (false) prophet and not a (false) christ. He's a prophet, not a messiah.
Do not assume the two are synonymous in the case of the beast.
All of these were contemporaries that occupied first-century times.
I completely agree John is writing about first century conditions, those leading up to, during, and soon following the city's destruction in 70 AD. None of that is in dispute. What is in dispute is the claim antichrists did not exist before or after John's epistles.
They did.
The one titled "THE Antichrist" was just like the other antichrists in his time with one exception: he would be the first to get into the second temple, showing himself to be God in that location. This was fulfilled by the Zealot leader Menahem back in AD 66.
This sign of the Man of lawlessness showing himself to be God in the temple would alert the believers that the time for the "gathering together" unto Christ was approaching for them - in that first-century generation, before it had passed away.
Don't digress. I am not interested and take at as an effort to avoid the point in dispute.
Perhaps this will clarify the issue:
The OT prophecy a virgin would bear a child are often debated because the original language can be translated "maiden" instead of "virgin." The problem with the "maiden" argument is there's nothing particularly unique
or prophetic about a young woman being pregnant or having a child. A virgin getting pregnant and having a child is unique and a prediction saying a virgin is going to have a child is something to look for
because of its uniqueness.
The reverse happens with John's commentary on the antichrists (plural). He explicitly states
many have come (plural and past-tense). Then he gives descriptions that are very commonplace.
- They deny Jesus is the Messiah.
- They deny the Father and the Son.
- They deny Jesus is from God.
- They deny Jesus came in the flesh.
There is nothing particularly unique about any four of those denials. Anyone could, at any time make any one or all four of those denials - especially if the reference to "came in the flesh" is a reference to the resurrection and not the incarnation. Men born into the world with flesh and blood is something that happens every day, but someone coming back from the dead, someone walking through the walls of a house and showing everyone in attendance his scars while declaring, "
See that I have flesh and bone," is very unique. Very easy to deny.
Part of the problem with this op and the ensuing discussion is that the John verses were selectively removed from their narratives. It's also very important to read, accept, believe, know and understand,
1 John 2:19
They went out from us, but they were not really of us; for if they had been of us, they would have remained with us; but they went out, so that it would be shown that they all are not of us.
Is the "
us," all converts to Christ? Or is the "
us" the apostles?

Do you see how often John said "they" in that one verse? There
many of them. ANYONE who denies Jesus is the Messiah is an antichrist. There were more people denying Jesus is the Messiah than there were believing he was the Messiah. But most of the gazillion people denying Jesus was the Messiah did not come from among the "
us."



How can anyone claim to know the antichrist if they have ignored the fact he/they came from among the "us."
This may be a problem for any of the Jewish Zealots preterists commonly argue were the lawless man (among whom I would count myself).
He came from among the Christians, not the Jews and not the Romans

.
It's not unusual for a young woman to get pregnant. It is not unusual or people or fallen angels to deny Jesus. It is the eccentricity that makes the prediction prophetic. It is the eccentricity that identifies the culprit

. In the case of the antichrist (as opposed to the virgin), the canon of scripture was closed before his identity was made known. Which, sadly, is why there is so much speculation. Even sadder, there are many among us (pun intended) who think the guy is still in our future.
I gotta go. I'll get back to this later if necessary.