Spiritually, yes it can be anyone or group whose behavior is diametrically opposed to the teachings of Christ. But usually "antichrist" refers to a specific apocalyptic individual who embodies Satan the way Jesus embodies God. There are a number of prophecies concerning the rise, activities, and destruction of this individual. Funny that Peter Thiel doesn't use either to describe his antichrist. He just makes shit up and calls it antichrist because that's what works on the hateful bigots of the maga base.

Many Baha'is believed the US Dollar was the antichrist for the US, because their definition of antichrist was anything that gets in the way of the masses finding their own spirituality. Then Trump got elected in 2016.....