Actually the peace process of the M19/UP of the 1980s is a chilling precedent of what will happen in Colombia if this agreement goes on: The government may grant immunity to the FARC, but their victims will not forget nor forgive.

Peace with impunity will mean more war, as the victims of the kidnapping, racketeering and murdering (or their surviving relatives) will want their revenge, just as they did after the government forgave M19's crimes.

In the (unlikely) case this agreement is approved, it wouldn't surprise me if it leads to a coup. And that's a rare thing in Colombia, one of the oldest democracies in the world and a country where the last coup attempt took place in the 19th century.