William Burkitt on 2 John 1:7

Having exhorted them to perseverence in the faith before, he subjoins a reason for that exhortation now, because many deceivers are entered into the world, &c. Many imposters were gone forth abroad, who denied, some of the divinity, others the humanity of Christ, and so razed the very foundations of Christianity, and thus discovered themselves to oppose Jesus Christ.

Learn hence, That even from the beginning our Lord Jesus has had those who have disowned his natures, and denied his offices, the divinity of his person, the meritoriousness of his satisfaction; these are antichrists, persons maliciously set against Christ, and they shall find him righteously set against them in the day when they shall be summoned by him solemnly to appear before him.