Enchant creature
Enchanted creature gets +2/+2 and can't block.
When Undying Rage is put into a graveyard from the battlefield, return Undying Rage to its owner's hand.
If the target creature is an illegal target by the time Undying Rage tries to resolve, it doesn't resolve. It's put into its owner's graveyard from the stack rather than from the battlefield, so its last ability won't trigger.