A season of American Horror Story is separate series itself but loosely connected previous seasons. In AHS: Apocalypse, we saw the Michael Langdon aka the anti christ wins but Mallory was able to go back in time and kill young Michael Langdon before he gains control of his powers. In the teaser for the new season titled AHS:1984, we see that the plot sets in 1980s and there will be more knives and stabbings than usual.
Where is the Anti Christ in all this?
To answer that, there probably won’t be Michael because he was born in 2011 but died in 2015 when Mallory ran over him with the car altering the timeline forever. Since the new season takes place in 1984, we will not see any trace of Michael. We might get reference to previous attempts by the Satan to create the Anti Christ or reference to serial killers like Beauty Queen Killer, Christopher Wilder.