What if, when Gaius Marius's request to be the commander against Mithridates in 88BC is denied, he flies into a fit of rage and has a stroke that kills him, instead of getting Tribune Rufus to basically dismantle the government through his vetoes and lawmaking? This action of Marius's part led to Sulla marching on Rome (the first time this ever happened), and the first civil war in Rome's history.
With this POD there are no murder's of Sulla's supporters, nor the infamous proscriptions of thousands of Marius's followers afterward. The Senate remains divided but united, and Sulla has all the monetary and material support he needs against Mithridates. He utterly thrashes Mithridates more easily, Rome sees an influx of loot from the East, and Sulla becomes an honored and feared elder statesman instead of a madman reviled as traitor and mass murderer.
Sulla can better and more solidly institute his reforms of Rome's taxation of her provinces, though the lack of massive cash from proscriptions means that his great public works are probably left undone. Crassus, Lucullus, Metellus Pius, and others' fortunes soar under his zenith while the careers of deviants such as Catilina and Ofella are butterflied, because there's nothing easy and treacherous to do without proscriptions.
Pompey...is a strange case. Sulla doesn't need his legions anymore and could easily crush the young man if he went rogue. Though Pompey's father might still be alive, because he didn't catch dysentery at the Siege of Rome in 87BC. Though being of a senatorial background and from (probably) the richest family in Italy, Pompey could become a great general...but legally, and at an older age.
Thoughts?