Erik and Charles were never adversaries. They addressed one other as "old pals." They never harmed or sought to kill each other, even when one was in the way of the other. Their conflict was more intellectual than physical.
When Erik was using his powers on a large scale, Charles wanted him removed from the planet because he was afraid that someone like Erik would tear down what Charles had worked so hard to create. But when the time came for Erik's departure, Charles helped him escape because he knew that he could be useful to him in another life. When Erik later returned to attack Genosha, it was with the intention of finding a cure for his mutant powers but not killing anyone else. Even after being severely wounded, he still tried to protect the people on Genosha from certain death.
Magneto hated humans for their prejudice and violence, but he also loved his brother so much that he would never harm him. When Erik left Earth, Magneto hoped that he would come across a peaceful planet where mutants could live in peace too. But once again, fate had different plans for Magneto. After being poisoned by Arnim Zola, who was working for Hitler, Magneto lost the will to live and decided to do something about it.
An adversary or foe is a person or group who is thought to be violently opposed or threatening. It has been noticed that the notion of an adversary is "fundamental for both people and groups." Adversaries can be real or perceived, but they must have the ability to harm your interest. Enemies are those who can do so intentionally.
The word "adversary" comes from the Latin adversus, meaning "against". In law, an adversary is a party against whom a right is asserted or a duty is owed. A judge will usually not decide in favor of one party over another, but instead decides between the parties based on what he or she considers to be the most important issue in the case. Similarly, a jury determines the outcome of an action by weighing the evidence and coming to a conclusion on which side they believe will win at trial.
In war, an adversary is someone who fights against you. This could be another country, but it often means people who fight under your own flag. During the American Civil War, the Union Army referred to the Confederates as its adversaries because they fought them directly rather than working within the system to improve their situation. Today, Americans use the term with respect to terrorists who threaten our way of life and seek to destroy us if we are successful.
Britain was both France's and America's mutual foe. French wars with Britain lasted from 1715 to 1815, when Napoleon signed a peace agreement that ended the war for good. The two countries remain diplomatic allies today.
France has had more than its share of enemies over the years, including Germany, Spain, Italy, Japan, and Russia. Today these enemies are the countries against which France fights for territory or influence.
During the French Revolution, France became an enemy of England, Germany, and their European colonies. In 1793, France went further by declaring war on Great Britain and its allies (including the United States). The British defeated France in 1814, ending two centuries of conflict between the two nations.
In World War I, France joined England, Belgium, and Serbia against Germany. In 1940, under German occupation, France became involved in the war against Germany. More recently, France has taken part in operations in Mali, the Central African Republic, and the Ivory Coast.
Germany was France's greatest enemy during the Cold War. However, after the fall of the Berlin Wall in 1989, Germany opened itself up to foreign trade and visitors.