It has completed itself.
Interesting and Hidden Aspects:
Jesus's last words from the cross in John. The word is much more interesting that it appears.
"It is finished" is translated from a Greek word, which means "to complete" and "to accomplish," especially in the sense of having goal. It also means "to bring to perfection." The voice is either the passive, "it has been completed" or the middle, "it has completed itself." Jesus is not saying that he did what was accomplished, but that the job was done and the goal reached.
The tense is the perfect tense. Indicating that something was not only started in the past but that is was completed in the past. In the English that the KJV uses, this would no be "it is finished," but "it has been finished." Or more accurately, "it has been completed" or "it has brought itself to perfection." Why is this interesting? Since Jesus has not yet died when he says this, he seems to be referring to his suffering being over. This makes it seem like his awareness of his suffering and humiliation was what needed to be accomplished.
Another interesting aspect of this statement is that it does not describe the resurrection, but his suffering. As I happen to write this on Easter, the perspective is interesting. Jesus knew that he would be raised. However, here he uses the word that means reaching a goal. The suggestion is that the goal of his life and maybe the goal of all our lives is to get through our suffering. The rewards after that are not truly the goal.