From the article on Wikipedia on Sulla, apparently Caesar was proscribed by Sulla and marked for execution. However, Sulla changed his mind and spared him.
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Sulla instituted a series of proscriptions (a program of executing those whom he perceived as enemies of the state). Plutarch states in his "Life" of Sulla (XXXI): "Sulla now began to make blood flow, and he filled the city with deaths without number or limit", further alleging that many of the murdered victims had nothing to do with Sulla, though Sulla killed them to "please his adherents".
"Sulla immediately proscribed eighty persons without communicating with any magistrate. As this caused a general murmur, he let one day pass, and then proscribed two hundred and twenty more, and again on the third day as many. In an harangue to the people, he said, with reference to these measures, that he had proscribed all he could think of, and as to those who now escaped his memory, he would proscribe them at some future time." -Plutarch, Life of Sulla (XXXI)
The proscriptions are widely perceived[by whom?] as a response to similar killings which Marius and Cinna had implemented while they controlled the Republic during Sulla's absence. Proscribing or outlawing every one of those whom he perceived to have acted against the best interests of the Republic while he was in the East, Sulla ordered some 1,500 nobles (i.e., senators and equites) executed, although it is estimated[by whom?] that as many as 9,000 people were killed.[15] The purge went on for several months. Helping or sheltering a proscribed person was punishable by death, while killing a proscribed person was rewarded with two talents. Family members of the proscribed were not excluded from punishment, and slaves were not excluded from rewards. As a result, "husbands were butchered in the arms of their wives, sons in the arms of their mothers".[16] The majority of the proscribed had not been enemies of Sulla, but instead were killed for their property, which was confiscated and auctioned off. The proceeds from auctioned property more than made up for the cost of rewarding those who killed the proscribed, making Sulla even wealthier. Possibly to protect himself from future political retribution, Sulla had the sons and grandsons of the proscribed banned from running for political office, a restriction not removed for over 30 years.
The young Caesar, as Cinna's son-in-law, became one of Sulla's targets and fled the city. He was saved through the efforts of his relatives, many of whom were Sulla's supporters, but Sulla noted in his memoirs that he regretted sparing Caesar's life, because of the young man's notorious ambition. The historian Suetonius records that when agreeing to spare Caesar, Sulla warned those who were pleading his case that he would become a danger to them in the future, saying: "In this Caesar there are many Mariuses."
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What would have happened had Sulla killed Caesar?