The shooting took place in a car park near the entrance of Bastia airport in the north of the Mediterranean island.
Two men opened fire, instantly killing Antoine Quilichini, an organised crime boss nicknamed “Tony the Butcher” who was convicted in 2016 of conspiring to murder the cousin of a mafia boss.
Jean-Luc Codaccioni, who was on leave from a Corsican prison where he was serving time over the same murder, was seriously wounded.
A third man sustained minor injuries after being grazed by a bullet, the public prosecutor in Bastia, Caroline Tharot, said.
A murder investigation has been launched.
Killings linked to gang violence and drug trafficking have claimed a number of lives in Corsica, where separatists waged a nearly four-decade bombing campaign before laying down arms in 2014.
Nationalists seeking greater autonomy for the mountainous island of 300,000 — birthplace of Napoleon — are tipped for big gains in the second round of regional elections Sunday.