Ocrop27 said:
For a second he ignites he’s light saber and think about not letting a second vader exist, but then realised what he was doing. That doesn’t make him fail as a jedi, since we already seen this same scenario in ROTJ where luke choses to not strike his father.

He did fail as a Jedi. For one Jedi are supposed to control their impulses, to think before they act. That’s the responsibility that goes with great power. Secondly, even if we accept this failing, he greatly compounds this failure by not attempting to fix his mistake. He realised what he was doing, and then turned his back on the galaxy and his friends. Snoke was able to strengthen his hold on Ben, and Luke’s failure to act, ultimately leads to the death of his friend Han, and the FO overrunning the galaxy. Remember, the entire premise of the ST is, that they need Luke Skywalker to achieve their goal of restoring freedom. The character of Luke Skywalker has been completely eviscerated, and for what? To replace him with another new hope, who unlike Luke get’s her power and status just handed to her.