Assalaamu alaykum. I was wondering why is Ad-Dajjaal called the Antichrist? Shouldn't he be called Anti-Mohammed (phub)?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

As far as we know, it is not stated in the Sharee'ah that Ad-Dajjaal is named as "Antichrist". However, there is no doubt that he is the enemy of Christ, the Son of Mary, may Allah exalt his mention; the enemy of the Prophet Muhammad ; and the enemy of every believer. But first and foremost, he is the enemy of Allah Almighty due to his disbelief. Allah Says (what means): {…then indeed, Allah is an enemy to the disbelievers.} [Quran 2:98]

For more benefit, please refer to Fatwa to kill the Dajjaal">138310.

Allah knows best.