The gospel reading for today recounts the troubling revelation of the betrayal of Christ by Judas. For me, Judas' very existence and the part he played in handing Jesus over to be condemned is a puzzle. Even the gospels treat Judas with varying degrees of culpability. John, being the most condemning, describes the Iscariot as a thief and motivated by pure greed, allowing for Satan to have influence over him. Matthew's Gospel is the most forgiving, recounting Judas' deep regret and desperate attempt to right his wrong with the chief priests before hanging himself.
In artwork, Judas' betrayal with a kiss is a compelling and often striking image. Christ's grief in losing one of the twelve is profound and heart wrenching. Regardless of his motivations, there is a lesson for us. The article discussing Judas Iscariot from New Advent communicates this lesson better than I could ever paraphrase:
". . .it may be urged that in exaggerating the original malice of Judas, or denying that there was even any good in him, we minimize or miss the lesson of this fall. The examples of the saints are lost on us if we think of them as being of another order without our human weaknesses. And in the same way it is a grave mistake to think of Judas as a demon without any elements of goodness and grace. In his fall is left a warning that even the great grace of the Apostolate and the familiar friendship of Jesus may be of no avail to one who is unfaithful. And, though nothing should be allowed to palliate the guilt of the great betrayal, it may become more intelligible if we think of it as the outcome of gradual failing in lesser things. So again the repentance may be taken to imply that the traitor deceived himself by a false hope that after all Christmight pass through the midst of His enemies as He had done before at the brow of the mountain. And though the circumstances of the death of the traitor give too much reason to fear the worst, the Sacred Text does not distinctly reject the possibility of real repentance."