Do you think there's something thats unforgivable?

I'm afraid you have a fundamental misunderstanding of Christianity and forgiveness. The Bible is quite clear. All I have fallen short. The wages of sin is death. No one 'deserves' forgiveness. Forgiveness comes by the grace of God alone. It is his desire that we live with Him and according to His ways, but he knows we can't on our own. Hence Jesus' death on the Cross which enables forgiveness if we accept that he took what should've been ours. Jesus had much to say about our reception of forgiveness causing us to be forgiving people.

Christians should be forgiving. No one deserves anything except death. However, we can point to the good news that there is a possibility of complete forgiveness before God for those who want it.

As for a line where I cannot forgive other people? In theory of course there shouldn't be one. But I would be lying if I said that I didn't find some things very hard to forgive. My best remedy then is to remember what I've been forgiven for and apply that to others. By the way, personal forgiveness is not the same as believing that people don't have to face the legal consequences of their actions. We have to have laws which keeps us safe, but we don't have to have personal bitterness towards those who have done us wrong. That would be self-inflicted poison.

Hope that helps.