Lancelot betrayed King Arthur primarily through his passionate, adulterous love affair with Queen Guinevere, which violated his oaths of loyalty, fractured the Round Table, and ultimately led to civil war, the downfall of Camelot, and Arthur's death at the hands of Mordred. While he loved Arthur as a king and friend, his overwhelming romantic feelings for Guinevere, often described as irresistible, superseded his duty, causing immense internal conflict and tragic consequences, notes Encyclopedia.com.
Guinevere cheats on her husband because she falls madly, passionately, desperately in love with Sir Lancelot. It is her role to be the femme fatale in the Arthurian canon. Its also very much in keeping with the medieval concept of courtly love.
Galahad is often depicted as the most trustworthy, while Lancelot is often trusted by Arthur until Arthur learns of his betrayal.
S1, E9: Sir Lancelot is banished from Camelot because King Arthur thinks he made a false claim against King Marhaus. Outside of Camelot, Lancelot encounters Marhaus and discovers an evil plot. S1, E9: Sir Lancelot is banished from Camelot because King Arthur thinks he made a false claim against King Marhaus.
Eventually, when Lancelot's adulterous affair with Guinevere is publicly discovered, it develops into a bloody civil war that, once exploited by Mordred, brings an end to Arthur's kingdom.
Lancelot sacrificed himself in Arthur's place to banish the Dorocha, leaving Arthur deeply saddened. He held a memorial for Lancelot and made a speech naming him as the noblest knight he'd ever known (The Darkest Hour).
Mordred kills King Arthur in every major version of the legend. The two fight a battle over the future rulership of Camelot in which they are both mortally wounded.
Lancelot is named after Lancelot of the Lake, one of the Knights of the Round Table in Arthurian mythology where he typically figures as King Arthur's greatest companion and one of his greatest knights, and his parents were King Ban of Benoic and Queen Elaine.
That said, the arc of the story leaves little doubt that Lancelot is far and away the strongest, with only Tristan and Lamorak (and Palomides on a very good day) even able to keep up in the tournament scene, so if we are to accept your assertion that Arthur is even with Mordred, that would certainly suggest that ...
Mordred was known to be Arthur's greatest enemy, sent to destroy him. His parents are Arthur's half-sister Morgause and Arthur himself. His step-father is King Lot of Orkney, and his half-brothers are the knights Gawain, Agravine, Gaheris, and Gareth.
In his eulogy, Stephen Langton, the Archbishop of Canterbury, referred to William Marshal as the greatest knight who had ever lived. But what's of particular note is that even his latter day enemy, Philip II of France, praised him.
The middle and upper tiers are devoted to the renewal of the search by Sir Galahad and its final consummation in the appearance of Our Lord with the Grail to Sir Galahad (upper center), Sir Bors (middle left center), Sir Percival (middle right center), and other knights prominent in the search.
Just to clarify for any readers in case there was any confusion, the three wives of Arthur in Welsh tradition were indeed named Guinevere (or rather, Gwenhwyfar), but the three mistresses had their own names.
Sir Lancelot was King Arthur's most trusted companion and loyal friend, but the closeness of their relationship made Lancelot's ultimate betrayal all the more painful.
Their Marriage
Arthur met his daughter Guinevere, and fell instantly in love. Merlin tried to persuade Arthur against marrying her, telling him that she would lead to his and his country's ruin. Arthur loved her too much, and married her anyway.
However, Mordred's faith in Arthur and Camelot was shattered after the imprisonment and death of his beloved Kara. Believing that Arthur had betrayed him and metaphorically spat on their friendship, Mordred turned against the king and joined Morgana once more.
In Welsh, Merlin's full real name is actually Myrddin Wynn Emrys. Myrddin is his first name, Wynn is his family name and Emrys is his druid name. In the original Arthurian legend, Mordrid and Arthur are half-brothers.
He is known for his super resilience due to his time spent in Purgatory, and formerly, his immortality which he gave up in order to resurrect Elaine.
No one was killed for Catherine of Aragon to marry Arthur, Prince of Wales. The two were betrothed as part of an agreement between their fathers, King Henry VII of England and King Ferdinand II of Aragon.
In the Tavola Ritonda, Camelot is abandoned and falls to ruin after the death of Arthur.
Later variants most often characterised Mordred as Arthur's villainous bastard son, born of an incestuous relationship with his half-sister, the queen of Lothian or Orkney named either Anna, Orcades, or Morgause.
Morgana Pendragon is the main antagonist of the BBC series, Merlin. She is the illegitimate daughter of Uther Pendragon and the half-sister of Arthur Pendragon and Morgause.
After developing a friendship with Merlin, she quickly becomes smitten with him (The Dragon's Call). Although Merlin is unaware of Gwen's feelings for him until she kisses him when she finds out he is alive, despite being poisoned (The Poisoned Chalice).
Lancelot was one of the Knights of the Round Table in the court of the legendary King Arthur. He was raised by the Lady of the Lake, who taught him to fight. Lancelot's most important relationships are his friendship with Arthur, his love affair with Guinevere, and his connection to his son, Galahad.