Because it was said to be a noble failure, since King Arthur and his knights were the best in the world.
People may feel proud when Lancelot defeats them in battle in "The Acts of King Arthur and His Noble Knights" because Lancelot is widely regarded as one of the greatest knights in Arthurian legend. Being defeated by a renowned and formidable opponent can be seen as a validation of one's own skill and courage. Additionally, it may also be seen as an honor to have been tested and bested by someone of Lancelot's caliber.
King Arthur killed Mordred at the Battle of Camlann. Arthur was fatally wounded in the battle.
King Arthur die in the Battle of the Saxon's
at the battle of Camlan Mordred either killed or fatally wounded Arthur
He and Arthur were having a battle, when Mordred delivered Arthur a fatal blow, and Mordrd also died.
Which battle? There are dozens of battles in the Morte d'Arthur.
Lancelot
Lancelot was known as the greatest and worst of the Knights. He becomes the King's Champion and undertakes quests in the King's name. He becomes the adulterous lover of Queen Guinevere, they have a son named Galahad. This relationship brings to an end the Court of King Arthur. Lancelot was the creation of Chretien de Troyes, written about in the late 1100's. Malory wrote about Lancelot 300 years later when he was presented as a much more popular Knight and became Arthur's favorite Knight. However, Arthur and Lancelot eventually kill each other in battle.
Sir Lancelot was a knight, and all knights used swords as weapons in battle.
Guinevere was married to King Arthur, so ruled over Sir Lancelot as Queen. Then, the two fell in love and had an affair, thus causing the Last Battle, in which King Arthur is slayed while trying to kill Lancelot.
Arthur's conflict with both Lancelot and Mordred involves betrayal by someone close to him. With Lancelot, it is a betrayal of loyalty as Lancelot has an affair with Queen Guinevere, causing strife within Arthur's kingdom. With Mordred, it is a betrayal of family as Mordred rebels against Arthur and eventually leads to Arthur's downfall in the Battle of Camlann. Both conflicts ultimately contribute to the unraveling of Arthur's kingdom.
In the King Arthur legends, the affair between Lancelot and Queen Guinevere caused a major rift in loyalty between the knights of the round table. There was lots of conflict and a siege in which Lancelot finally gave up Guinevere to King Arthur. Lots of the central knights were killed either accidentally or intentionally during this bout when trying to capture Lancelot and when Lancelot rescues Guinevere from execution. Mordred and Morgana Le Fay/ Morrigan Le Fay, were basically brewing up this whole conspiracy so that they could overthrow the king. There is a grand final battle, and Arthur loses. He is sent off to Avalon, the land of the elves, and is rumored to come back when the people of Britain need him most.
Arthur's last battle is usually reckoned to be Camlann - provisionally dated to 537 AD.
No one. When Arthur fought the last battle against Mordred, Camelot collapsed. Lancelot, because of his sin of adultery, joined a monastery to seek forgiveness. He gives up his wordly ways. And the realm Arthur had worked so hard to forge dies away.
Because Sir Gawain believed that King Arthur and Sir Mordred were poorly matched. Sir Gawain did not believe King Arthur could win the battle without help from Lancelot, and thus a month-long treaty would allow enough time for Lancelot to return and help usher King Arthur to victory over Mordred.
Sir Lancelot would usually use a sword.
There are no easy, quick fix answers when dealing with Arthurian literature and the Arthurian legend. In general, Guinevere goes to a convent at some point before Arthur's final battle at Camlann against Modred: it depends on which version you're reading. In some versions, Modred falsely proclaims that Arthur is dead and tries to marry Guinevere. There is one version where she actually does wed Modred. But mostly she resists him and winds up in the convent. Lancelot is said to try to help Arthur in the final battle against Modred at Camlann, only coming too late. He then goes to Guinevere in her convent and tries to kiss her, even for one last time. But she remains true to her new vow as a nun and is truly repentant for her love of Lancelot. She refuses his kiss. Lancelot goes off and becomes a priest. Sometime later, Lancelot has an urge to visit Guinevere one last time and goes to the convent, only to be told that she had died a short time before his arrival. So Lancelot takes Guinevere's body to be buried with Arthur. And not long after this, Lancelot himself dies.
King Arthur was killed by his son, Mordred of Orkney. Mordred was his son by his half sister Morgaine (Morgana) depends upon which author you're reading. In other legends, Mordred was a Druid.