I don't think that this is what you're looking for, but I'd suggest that you start with somebody like John the Baptist.
I mean, consider the following:
His coming birth was announced by an angel (Luke 1:13).
He leapt for joy in Elizabeth's womb at the sound of the mother of his Lord's voice (Luke 1:40-44).
He was the prophesied messenger of the Lord who was to prepare Jesus' way before him (Mark 1:2, Malachi 3:1) and/or the one prophesied to prepare the way of the Lord and to make his paths straight (Mark 1:3, Isaiah 40:3).
He recognized Jesus as "the Lamb of God which takes away the sin of the world" (John 1:29).
He baptized Jesus and saw the Holy Ghost descending upon him like a dove while hearing God's voice out of heaven testify of Jesus "You are my beloved Son; in you I am well pleased" (Luke 3:21-22).
He recognized that Jesus was the "Christ" (John 3:28) and "the bridegroom" (John 3:29), and that he "came from heaven" (John 3:31).
He recognized that Jesus not only "spoke the words of God", but that "God gave not the Spirit by measure unto him" (John 3:34).
He also plainly testified in relation to Jesus that "he that believes on the Son has everlasting life: and he that believes not the Son shall not see life; but the wrath of God abides on him" (John 3:36).
I mean, if anybody had faith in Christ, then John the Baptist was seemingly at the top of that list.
Here's the thing, though...
Notice what happened near the end of John the Baptist's life:
Matthew chapter 11
[2] Now when John had heard in the prison the works of Christ, he sent two of his disciples,
[3] And said unto him, Art thou he that should come, or do we look for another?
[4] Jesus answered and said unto them, Go and shew John again those things which ye do hear and see:
[5] The blind receive their sight, and the lame walk, the lepers are cleansed, and the deaf hear, the dead are raised up, and the poor have the gospel preached to them.
[6] And blessed is he, whosoever shall not be offended in me.
In other words, in spite of all that he had seen and heard, John had doubts near the end of his life.
Anyhow, it's not unusual for people of faith to experience doubt at times, and especially in times of great persecution.