Quote Originally Posted by Somebody Else
Most interesting - Octavian, though he should burn in hell for all eternity for destroying the Republic, as should J.C. and the rest for bringing it about.

Favourite - I'm going to join Baba Ga'on with Lucullus; great general, instrumental in defeating Mithradates (though Pompey stole all the glory) who was betrayed by his men and his peers. Possibly also Cassius and/or Brutus - for trying to restore the Republic (though, IMHO, Brutus was an idiot).
The rise of the Roman Empire was inevitable. Julius Caesar and Octavian aside the Republic was destined to be dissolved or rendered irrelevant one way or another. The fact that one bold, audacious man could send the Republic tumbling down like a house of cards speaks volumes as to the validity and stability of the Roman government at that time.

One could also argue that the excellent Marian Reforms helped hasten the end of the Republic. Marius may have created one of the most effective military machines in history but he also created an entity whose loyalties to the state became questionable. In the post-Marian era expediency and the needs of Rome's ever expanding borders often demanded that these armies be funded in part or entirely by the generals who led them. In most cases these generals were actual statesmen who, by nature of their personal ambitions, created reasons for Rome to go to war so that they could raise a personal army and conquer with the intent of accumulating more power and glory. The fact that the average Legionary became highly dependent on his general and benefactor for pay, incentives and his very survival meant that it was simply a matter of time before the man who controlled the largest and most effective Roman army ultimately became the man who ruled Rome.