Originally posted by crisis_ryitua
Caedus tortured Luke's son, murdered his wife, and threatened to kill Jedi children and still Luke let him walk.
Caedus: Luke's beloved Nephew who fell to the Dark side because of foolishness - not because he was truly evil.
What would happen if he succeeded: A second Empire would be born, some people would die; others be enslaved, and some people would live and still be free. The galaxy at large would still be relatively safe; no more in danger than the last Empire that inhabited it. Same as always.
Desann: A space-lizard who had no important connection to Luke. Who was also deliberately evil, from the get-go.
What would happen if he succeeded: Desann would absorb the power of the Valley of the Jedi - effectively making him invincable.
Trillions of innocent people could die instantly because of him.
The Force of thousands of Jedi is trapped here. If Jerec captures this power, he will be a creature such as the universe has never seen.
A supernova of stars in a fleeting thought—the eradication of life from a star system in a whisper—will be within his power."
―Qu Rahn
Unbeatable from that point on, Desann would irreversibly murder Luke's entire family and could go on a killing spree - wiping out all life in the universe, if he felt cast-out by them enough.
So it's either kill Desann - or watch him murder your family.
Unless Luke really valued Desann over Leia and her children - or Luke had some kind of secret romantic involvment with Desann - Luke basically lost fair and square.
There is no between here - unless Luke used his TK to either over-ride Desann's and slam his head into a wall - knocking him out mercifully or else just fling some debris at Desann's head, knocking him out mercifully.
But he could not do that. He was not capable of doing that to Desann. And doing that would not only simply end the threat, but do so in a merciful way. And Luke was not able to do that. Because Desann was too fast and powerful - and Luke Could Not beat him.
Luke did not try to turn Desann back during their fight, either.
And with Caedus, Blood is always thicker than water.
Originally posted by crisis_ryitua
Likewise, with all due respect, there is no reason to believe that Desann or Kyle are superior combatants to Luke when they lack his power and training.
With Desann training for only 1 year, Luke should have been able to easily disable him without hurting him too badly - but he wasn't good enough to do that.