Board Thread:Series 5 Discussion/@comment-84.84.54.179-20121017214129/@comment-2A02:587:C410:3B00:C9F8:F858:CA80:4D1-20171116043733

I believe he is genually good. In the end, I think he lost his trust in Arthur; in the begining he put his trust in him, as a just king who would eventually bring back sorcery (perhaps with laws that control it instead of banning it altogether), also following Merlin's example.

Because of Merlin not being close to him and/or trusting him, he never really understood what was expected of him, eventhough he tried. That said, he eventually reached his limit when Arthur had his Love interest executed; I do not believe that was the real reason, he already had doubts, but he wanted to believe in Arthur's ideals.

Ultimatelly, just like Morgana, Mordred is a cause of a self-fullfilling profecy; If Merling never knew of the profecy, and trusted Morgana with his secret and guided her, and latter was not cold towards Mordread and guided him the whole profecy could have been prevented. This is well hinted when Merlin says that he does not wish for more knowlage (of the future) from the Deomere, and does not like looking into the Crystals into the Crystal Cave, eventhough he has talent in predicting the future; Wile there is not one future, he sees the most probable future, and the knowlage he receives influances the outcome into sealing that future.