One among many heuristics I employ to relate figures in the history of thought is assuming that thinkers react to what is too prevalent in their own time, and try to balance things out by throwing their weight in the opposite direction. This heuristic has certain limitations, but like all heuristics it allows the history to come to light in a particular way that can be helpful. When considering what themes are 'balanced out' we come across some that are prominent and can be to an extent generalized across history. Such themes are one vs many and being vs becoming. These disputes may have their first classical exemplification in the West through the conflict of Parmenides and Heraclitus.
There are other thinkers in the history of thought that are interested in this heuristic. For example, Nietzsche seems to consider all culture and psychology as dealing in terms of these alterations from one extreme to another, and treats this as a problem to be resolved or at least understood. Recognizing this in my recent study of Nietzsche led me to consider what Heidegger means when he said Nietzsche brought Western Metaphysics to its completion (Heidegger himself offers other interpretations of this, such as in his essay on Plato's Doctrine of Truth). So far as I can see this alternation of one extreme to another, and the attempt by Nietzsche to overcome this, is what the remark means. While Nietzsche does seem to bring the history of Western Metaphysics to a close, it is only if we regard it in terms of the heuristic I mention above. Factually speaking, this back and forth still occurs and probably always will.
The concept of revenge is important for the notion of the superman and the will to power which play central roles in (this reading of) Nietzsche as completing Western Metaphysics. The superman is one who has overcome revenge; this being has transcended by no longer being a part of the constant back and forth; someone who has courage to stand on their own. This I read as the ideal of the overcoming of the back and forth. The will to power is generally a fundamental striving to overcome opposition. This usually is characterized by overcoming external forces or agents, but the most crucial opposition we face, the most primary and difficult to dominate, is ourselves.
When we take the will to power as the highest metaphysical principle, then it can direct our attention to that which leads us to struggle with things that are external, and shed light on how opposing others is a weakness of character; we ignore the most difficult and closest opponent that actually has dominated us in these struggles with external opponents - ourselves. It takes great magnanimity to preserve ourselves in the face of others.
How does this finish the history of Western Metaphysics? The reason why Nietzsche brings the history of metaphysics to a close is not because it makes up for something in any of the (apparently) different systems of thinking, but because it makes their apparent opposition a problem that is resolved with the highest principle in Nietzsche's system: will to power. Of course, this brief sketch cannot be the end of the full importance of Nietzsche, but rather is only an attempt to consider him in the light of the heuristic of reacting to what is too common.