Anakin Skywalker had many faults which the Jedi Council were concerned about: fear, anger, aggression, and it was heavily hinted towards the end of The Clone Wars that some of the Masters were aware of, or at least suspicious of, his relationship with Amidala. Even Anakin’s own padawan knew the truth.
Of all of those faults, though, the one thing we saw over and over again was that Anakin never followed the Jedi edict to use the Force for protection, for defense; whenever there was even the slightest conflict, his lightsaber always came out quickly, and later on, he would even tap into the Dark Side to choke Ventress.
Something that struck me while I was watching Empire Strikes Back recently (for about the thousandth time), was that when Luke confronts Vader in Cloud City, Luke draws his lightsaber first, just in the manner that Anakin always used to do, directly against Master Yoda’s warming to never use the Force for attack.
Vader simply stands silently for a few seconds before igniting his own weapon. Now, I realize that all that I said about Anakin, his time as a Jedi, was written well after ESB, but to me, that is so utterly perfect. The writers of the later material so perfectly analyzed that confrontation in the Carbon Freezing Chamber that they wrote their material to show a greater subtext to the scene. Luke is truly in danger of falling to the Dark Side, just through the simple act of igniting his lightsaber first in the duel... and Vader knows it.
Somewhere along the way, Vader rid himself of his aggressive nature and truly became the Master, while his son was the hot-tempered learner.
Now, the circle truly was complete.