This is a strange little story. It is the only example of what might be called a negative miracle in Matthew. To our modern sensibilities it seems as if Jesus was ticked off about the fig tree and cursed it in a fit of pique.
On the outside, Jesus uses this as an acted parable to teach the disciples something about prayer. But there is probably also a deeper lesson. God will judge his people for their unfaithfulness.
This is a rare time during this week when we see Jesus alone with his disciples. The disciples marvel, as would I, when the fig tree withers before their eyes. It seems like they are asking Jesus what lesson they can learn. Jesus uses the common trope of moving mountains—in this case the Mount of Olives, on which they are standing—by means of prayer.
It is natural to take the idea of praying for mountains to move as asking for difficult or impossible things, and I believe that is the idea that Jesus has in mind. All prayer to God must be aligned with his will. As far as I know, we can’t talk God into doing things that would go against the good of his kingdom.
This passage is certainly not encouraging us to pray for enemies to be removed or harmed.
Also, we must not get the impression that only great heroes of faith can get such prayers answered. When we line up with God, we are lining up with the great power of the universe. There is no power in the prayer itself, but there is great power in God.
So we grow in faith a little at a time. Faith is not a goal in which we can be proud of ourselves. It is really just us learning to trust God more and more.