The Mechanic

Everyone believes Leonardo Vega is just an old mechanic. They're wrong. By day, he repairs broken engines in a forgotten garage on the outskirts of Madrid. Grease-stained overalls, empty bottles, and a life that looks like quiet failure. But five years ago, the world buried a man known only as El Matador-one of Spain's deadliest covert operatives. Now the cartel responsible for his son's murder has made one fatal mistake.
They reminded him who he used to be. As gang leaders vanish, safehouses become slaughterhouses, and an entire criminal empire begins to collapse, an elite intelligence officer finds herself hunting a ghost everyone believed was dead. Behind the bloodshed lies a conspiracy reaching from the streets of Madrid to the highest levels of government. Outnumbered, outgunned, and armed with nothing but years of military training and an unbreakable promise to his son, Leo begins a war that cannot end until everyone responsible has paid.
Because some men carry guns. The Mechanic brings a sledgehammer.