Acts 8:3
As for Saul, he made havoc of the church, entering every house, and dragging off men and women, committing them to prison.

Other than Satan, there was never a greater enemy of the church than Saul of Tarsus. He was totally devoted to Judaism and saw Christianity as a threat and a lie against God.
Many others were enemies of the church over the years and some committed great atrocities.
But I view Saul as the first.
The church has always been persecuted, as has every faith and religion.
Even among Christianity one denomination will persecute another for the sake of believe one way is right and another wrong.
While I am a Christian I want to tell you about Christ, I am not apt to kill you if you disagree with me or reject Christ.
I do not mind others sharing their faith with me but I want the same respect when I reject their faith.
I do not see other religions and faiths as a threat to Christianity. But evidently others see Christianity as a threat to them.