
First, credit where credit is due, to Tar_Ranth for his great blog "Lightsabres--How Did Luke Build One?" (see it at blogs.starwars.com/hunterspride/5).
On that blog I mentioned that I never thought it was such an advanced skill for a Jedi to know how to construct a lightsaber. For years when I have heard Vader say: "I see you have constructed a new lightsaber...indeed, you are powerful as the Emperor has foreseen." That this was just merely a sign of how little training Anakin had received, or how far he had to go. Perhaps this was his own doing. As a child and young adult, Anakin, as we have seen in the Prequels, didn't listen very well to Qui-Gon or Obi-Wan. Even when he did, he seemed to twist their meaning (as earler as TPM when Anakin says to Artoo "Qui-Gon told me to stay RIGHT HERE and that's what I'm gonna do", as the ship he was in was taking off).
However, I think blame must also be placed on Palpatine. After Anakin's "death" and Vader's "birth" Palpatine wanted Vader to be a figurehead of the Sith's power, but HE--as the Emperor--wanted ultimate, unlimited power. Therefore, whatever Dark Side/Sith skills he might have given Vader, they paled in comparison to his own.
So, if that's the case, some of you are asking, why was Vader such a big deal? Why was he such a threat to Leia, Han, and the others? The same way a snake is a threat when a lion isn't around. Vader, to most people, was the only game in town. There were no more Jedi. Vader existed on the myth of previous Jedi and Sith and those memories of what others in the past could do haunted the galactic citizens and kept them in line.
In "Jedi" Palpatine says to Luke: "Young fool, only NOW, at the END do you understand" and then zaps him with Force lightning. Could he have been talking to the budding good in Vader/Anakin as well?
Think about it, whenever Darth Vader sensed anger or hatred in Luke he felt power, but Luke was the most powerful when he didn't use his anger or hatred, but his love. His love prevented him from fighting his father and even his father's evil master (because evil or not, Palpatine was the only stability Vader knew for the last twenty years).
Perhaps the Emperor was saying to Vader: "Young fool, only now, at the end do you see that love is the most powerful." "Young fool", becuase Palpatine thought it was surely too late for Luke. His father would not turn and Luke's sacrifice would be in vain.
But Luke didn't die. He took much more than Mace, or anyone else that had a jolt of Force lightning (Yoda kept it back, but Luke actually took it in) and survived. This is why I believe Luke IS the strongest of all Jedi. His father, Anakin Skywalker locked inside the Darth Vader carcass, could stand no more, and destroyed the Emperor, the embodient of hate, predjuice, and evil, to save his son, who, towards Anakin, was nothing but love.
"Vader doesn't want you at all, he's after someone called Skywalker"
--Lando Calrissian
Indeed, he was after someone called Skywalker, he was always hoping to find Anakin Skywalker again.