Lack of motivation
There is no reasonable explanation of Judas's betrayal. He had first hand experience of Jesus, his miracles and his teachings. It is not clear that Judas doubted Jesus. Judas was offered Mark 14:10-11 or requested Matthew 26:15 money to betray Jesus. It seems strange to consider betraying Jesus, a miracle working living God, for relatively little gain.
- Did Judas have free will to betray Jesus?
- Did Judas get sent to hell as a necessary step for God's plan of atonement?
- Did Judas suffer more than Jesus as part of this plan?
Acts records that Judas used the reward for the betrayal to purchase a field. His death seems to be a divine punishment since people normally do not burst open after a fall.
"Now this man obtained a field with the reward of his iniquity; and falling headlong, he burst asunder in the midst, and all his bowels gushed out."
In contrast, Matthew tells Judas expressed remorse, returns the reward and commits suicide:
"And he cast down the pieces of silver into the sanctuary, and departed; and he went away and hanged himself."
These verses have multiple contradictions:
- Judas returns the reward in one version and spends it in another. Apologists claims that the cast the money down on the sanctury floor, then reclaimed it and spend it on the field.  This is stretching interpretation beyond reasonable bounds.
- Judas dies by bursting open and he died by hanging. Some apologists claim that Judas hung himself, partially decomposed and falling, burst open. 
- Judas expresses remorse in one version and in the other he apparently doesn't. 
- God expressed his wrath to kill Judas in one version and in the other, Judas's death is self-inflicted. 
"It seems to me that [the death of Judas] and [inclusion of some unhistorical narratives] rule out the view that every statement in Scripture must be historical truth."