The Antichrist is often wrongly assumed to be an anti-Christian - like the majority of modern political, business, and other leaders in The West. But the idea is meant to convey a person who is superficially, apparently Christian - who therefore gathers the support of Christians... and then leads them into deceieved but self-chosen damnation.
Also, there need not be one Antichrist - but a multitude - it can be a type rather than a group.
How to penetrate the deception? Well it is seldom a matter of false doctrine - because doctrine is easily faked or distorted - the world is full of people who advertise that they are doing X, but interpreting matters so that they instead destroy X - and humans are very vulnerable to that kind of deception at all levels: the own-nation-hating patriotic politician, the women-destroying feminist, the pro-science advocate who converts research into bureaucracy; the doctor who causes sickness; the educationalists who transform teaching into form-filling...
So good doctrine is compatible with being Antichrist; while on the other hand 'bad' Christian doctrine seems perfectly compatible with true Christian status, in that real, exemplary Christians are found in many churches and denominations.
No - what makes Antichrist, and what makes Antichrist detectable, is any kind of Christianity pursued with unChristian motivation.
I say 'detectable'; but of course detecting motivation is a matter of intuitive inference, which each must do for himself (or else take the word of somebody he intuitively trusts as being both well-motivated and sufficiently informed).
In sum, we should not accept Christian leadership from anyone who does not place Christianity first, and foremost, as the priority in life (and repents their failures to live-up to this ideal).
The danger is that in today's climate, even someone who is merely interested-in and lukewarmly-supportive-of Christianity (perhaps as a means to an end of a more peaceful and prosperous society), might be set-up by Christian followers, out of a kind-of desperation.
Since this leader is, as a matter of fact, Not primarily motivated by Christianity - he will then use Christianity as a means to socio-political-business ends - as well as to fulfil personal goals such as status, sex, wealth etc. Since he is a leader, he will draw his followers down the same path - thus Christianity is made secondary, redefined expediently, evaluated in materialistic and worldly terms.
And this is an Antichrist, one of many - although not The Antichrist. I expect several names have come to mind as you read this - and names of not-bad, not-the-worst people... well, they (and not the obvious baddies) are indeed the Antichrists of our time.