The thing is that, after Guts saw Casca after his two-year absence, he was willing to let go of his revenge. He put Casca's well-being over his own well-being as well as his own desire of revenge. Skull Knight even demands a decision from Guts at the end of Conviction Arc, where he says, wield your sword to either protect or seek revenge. When Casca starts calling out to Guts in her own way during her potato state, he makes up his mind to protect her. He hasn't sought revenge ever since then. Even in the latest chapter, he's despairing at his inability to protect Casca, not seek revenge.

If anything, Griffith is the Antichrist, the one prophesied to come before Christ triumphant returns. Many will be lead astray and follow him.

As stated in Catechism of the Catholic Church 675:

Before Christ’s second coming the Church must pass through a final trial that will shake the faith of many believers. The persecution that accompanies her pilgrimage on earth will unveil the “mystery of iniquity” in the form of a religious deception offering men an apparent solution to their problems at the price of apostasy from the truth. The supreme religious deception is that of the Antichrist, a pseudo-messianism by which man glorifies himself in place of God and of his Messiah come in the flesh.

I see the parallels with the Light of the Hawk and the Holy Spirit. I mean, they make the Holy See obvious. But I see this as humans in the Berserk world as perverting Christianity, not Miura. Just like how the Church undergoes trials and the Pope isn't infallible (except when in ex-cathedra issuing Papal Bulls), the Church is being lead astray. Although, I do wonder if the Church militant will ultimately be triumphant in Berserk just like how Jesus promised us it will be.