Judas was repentant in the end.

Then Judas, His betrayer, seeing that He had been condemned, was remorseful and brought back the thirty pieces of silver to the chief priests and elders, saying, "I have sinned by betraying innocent blood." And they said, "What is that to us? You see to it!" Then he threw down the pieces of silver in the temple and departed, and went and hanged himself.  (Matthew 27:3-5)

I've seen nothing to suggest Marx felt similarly at the end of his life.