Shinzon

Shinzon was a Romulan-created clone of Jean-Luc Picard, intended for the purpose of infiltrating Starfleet. When the Romulans abandoned this plan, they exiled Shinzon to the dilithium mines of Remus. Eventually Shinzon led a Reman struggle for freedom, allowing him to briefly take over Romulus as praetor. This brought him into conflict with Picard in 2379, resulting in Shinzon's death. 

In the Pendragon timeline, there was no Dominion War to take Shinzon away from Remus. He would have died in the dilithium mines, were it not for another regime change in the Romulan Star Empire in the mid 2370s.

The Continuing Committee revisited Narviat's plan to infiltrate the Federation, and came up with a variant strategy. To that end, they had Shinzon liberated from the Reman mines, and Tal Shiar geneticists managed to reverse the cellular damage.

Shinzon began training as a Tal Shiar assassin, eventually alongside of other members of his cloning creche.