Sir Lancelot du Lac
Father of Sir Galahad. Son of King Ban of Benwick.
As a Young Adult
Though neither Lancelot or Guinevere let their affair get out of hand, they were eventually found out and Guinevere was almost burned at the state for adultery. Once, even, a young princess (Elaine of Astolat, who later died of a broken heart) pretended to be Queen Guinevere and gave Sir Lancelot a son: Galahad. This infuriated Queen Guinevere and soon King Arthur found out about the affair between the two, but still held Lancelot as his favourite, though Lancelot's relations with the nephew of King Arthur, Gawaine, dwindled quickly. Some even say that the young knight wished revenge on Lancelot.
Lancelot Du Lac
Strong, Courageous, Gracious, Gentle, Trustworthy, Helpful
The Death of Sir Lancelot
After Lancelot was shunned by Guinevere and a battle ensued between Arthur and he, Lancelot became angry and mentally and emotionally compromised. He walked the forests for months until he happened upon the Holy Grail; which he was only allowed a glimpse of because of his sins.
When he returned to Camelot, he found Arthur had died, and Guinevere gone to become a nun after telling Lancelot that she would never see her face again. Lancelot left Camelot and became a hermit in penitence with a few of his kin, eventually become a priest and tending to Guinevere's body after she died.
Also, a lot of what I had came from my memory and what I already knew.