Might as well throw out the Carthage option as it's potential that the mercenary war was purposefully initiated by the Romans.
Carthage had employed a relatively large mercenary army on Sicily during the first punic war. However there was no major land battle on Sicily (Rome forced Carthage to peace with the actions of their fleet) and Hamilcar Barca (The Carthage general in Sicily) was forced to a peace despite his army being 'undefeated' on the land. Hamilcar made a few promises to his mercs of great pay for their services...when an army hires mercenaries it in part relies on attrition, less surviving mercenaries is ultimately less people to pay. Since there was no major land battle, most of the mercenaries survived the journey back to demand pay which Hamilcar had promised earlier.
The last condition is mentioned by Polybius in place of the one regarding not making war on Syracuse. It is possible that Hamilcar Barca secured the last clause after the initial conditions, which were more favorable to Carthage, was altered by Rome with a harsher one. Hamilcar Barca gathered the Carthaginian soldiers from Drepana and Eryx at Lilybaeum, surrendered his command, returned to Carthage and retired to private life, leaving Gisco and the Carthaginian government to pay off his soldiers. Whatever was the motivation behind this act, it was resented by the mercenaries left behind in Sicily.
Hard to call if avoiding a direct land engagement was intentional by the Romans (This was before the Fabian strategy was used vs Hannibal where the Romans intentionally avoided a direct battle with Hannibal), however the end result was the majority of the mercenaries survived the Punic war to return to Carthage where they would demand pay.
The “Undefeated” army now created a unique problem for Carthage. Had Hamilcar suffered a decisive defeat, casualties and prisoners would have diminished their numbers and Carthage would have had an excuse not to pay anything. But now the 20,000 man army had to be paid their full due.
The peace arrangement with Rome included a hefty amount in war reparations to Rome which heavily impacted Carthage's ability to pay these mercenaries. The mercenaries were sent in small groups to Carthage to be paid, but the Carthage gov't couldnt and the number of unpaid mercs in Carthage grew.
Carthaginian authorities then sent them off to Sicca, planning to plead with the whole army to forgo their unpaid wages by pointing out the dire financial situation of Carthage. Hamilcar’s former soldiers, who had been kept together only by his personal authority and by the promise of good pay, broke out into open mutiny once Hanno the Great tried to impose this, and marched on Carthage and encamped at Tunis. The soldiers refused to accept Hamilcar as an arbitrator, angered by his refusal to accompany his army from Sicily and retiring to Carthage as soon the treaty with Rome was formalized, and although Carthage at this point conceded all their demands, things soon boiled over and started the conflict known as the Mercenary War
The mercenaries found like minded African subjects of Carthage and the mercenary war began.
As an interesting side note...the Punic wars was actually initiated by Mercenaries dragging Carthage and Rome into conflict. A group of mercenaries known as the Mamertines was employed by the Greek city state of Syracuse to fight vs the Carthaginians. The Greeks were defeated and when the self-proclaimed king died, the majority of his mercenaries found themselves unemployed on the island of Sicily. The town of Messana let the mercs in and the mercs betrayed them and slaughtered the population turning the town from a small farm town into a raiding base. The new king of Syracuse saw this threat and marched against the Mamertines and defeated them. The Mamertines plead with both Carthage and Rome for help, ultimately bringing Rome and Carthage into the conflict known as the first Punic War.