The central twist of "Vincenzo" is the identity of the true chairman of Babel Group. For the first third of the series, the goofy and seemingly harmless intern Jang Joon-woo is a background character with a crush on Hong Cha-young. The shocking reveal in Episode 8 that he is actually Jang Han-seok, the sadistic and sociopathic mastermind, completely changes the dynamic of the show. His cowardly older brother, Jang Han-seo, who was presented as the chairman, is merely his puppet.
Another key plot point is the true identity of the gold. It is stored in a secret, biometric-secured vault underneath Geumga Plaza, placed there by a deceased Chinese tycoon. Vincenzo's primary mission is to retrieve it, but the tenants' refusal to leave and Babel's takeover prevent him. The gold, named the "Guillotine File," is later revealed to contain not just gold bars but also a flash drive with incriminating evidence on all of South Korea's most powerful figures, making it the ultimate weapon.
The finale provides a dark but cathartic resolution. Vincenzo does not get a purely happy ending in the traditional sense. After his mother is killed, he fully unleashes his mafia persona. He subjects Choi Myung-hee to a gruesome death by having her be doused in water on a mechanical platform while she's forced to dance Zumba, a hobby she loved, until she's electrocuted. He then enacts his ultimate revenge on Jang Han-seok, using a tool he calls the 'Spear of Atonement'—a drill that slowly impales him over the course of a day. Having exacted his revenge, Vincenzo is forced to flee Korea. The final scene shows him as a mafia boss on a Maltese island, where he reunites briefly with Hong Cha-young, confirming he will continue to live as a 'villain' who fights for his own brand of justice.