- "Sergei Voronov is a young Russian punk, a post-glasnost thug, looking to make a name for himself apart from the established godfathers. His father is a powerful ex-KGB crime lord from Moscow. He is desperate to prove he's smarter, tougher, and better than everybody else out there."
- — Mercenaries: Playground of Destruction game manual
Sergei Voronov is the eccentric, erratic and possibly unstable leader of the Russian Mafia for a majority of the campaign in Mercenaries: Playground of Destruction. He is also the administrator of a black-market website, Merchant of Menace, run by the Mafia.
- "(sniff) Hey, alright! Just what I need, a professional! My name is Sergei Voronov, and this is my lieutenant Josef. We run the, uh, discreet supply business around here. Everyone here needs stuff: vehicles, weapons, you name it and we supply it. Discreetly!"
- — Sergei upon meeting the mercenary
Sergei is the head of the Russian Mafia when the mercenary is first introduced to the faction. He is assisted by Josef Yurinov, apparently sent not only to aid Sergei but also to monitor him and correct his mistakes. Sergei gives the Mercenary increasingly bold missions throughout the game, possibly because he wants to show off and achieve his goals as quickly as possible, and doesn't care how he does it.
- "I'll kill anyone who betrays my trust! You got a problem with that? You got a problem working for a killer!? (cocks pistol) Huh? Answer me! (Josef yanks his gun away and whispers to him) ... Ahaha, Josef is right."
- — Sergei overreacting
Sergei is highly erratic, talkative, careless, and drastically paranoid. He frequently overreacts or threatens to kill the mercenary or anyone else over a real or imagined insult or threat. He also has a very short memory span, forgetting things from movies he's seen, what he or other people have been doing, and even things he's told the mercenary at the beginning of a conversation, leading to him repeating things and being corrected by Josef. He commonly forgets or mispronounces names, although it's unclear whether this is because of his forgetfulness or simply a lack of skill in using other languages' pronunciation. He often overestimates himself despite his paranoia and obvious inexperience, and can be heard trying to talk up his operation to an unidentified higher-up on the phone (possibly his father).
During the last quarter of the game, Sergei's growing paranoia drives him to make the ill-founded decision to betray both Josef and the mercenary to the North Koreans, believing that they would betray him first. Ironically enough, it is this move that causes them to actually betray him in turn, and may even lead to his death if the player so chooses.
Sergei has little respect for any of the other factions and belittles them equally. He is also quite rash as he assigns the mercenary with the job of killing an AN officer and a Chinese commander, apparently unaware of the fact that both factions are vastly superior to his own in terms of resources and equipment and could easily destroy him if need be. He views anyone who stands in his way as an enemy that must be removed, and rarely mentions any of the opposing leaders personally. He does, however, mention Agent Buford by name in one mission against the South Koreans, in which he humorously mispronounces his name as "Boo-ford."
- It can be inferred, due to his frequent sniffing and snorting, that Sergei uses-- and very likely abuses--cocaine. This would at least partially account for his behavior.
- Sergei is a fan of mobster movies; specifically The Godfather . He tries to emulate Marlon Brando's character from the film, though he mistakenly believes his pet is a monkey rather than a cat. This leads to a rather humorous rant to Josef in Russian that concludes with Sergei demanding that someone get him a monkey.
- Sergei is the only character in Mercenaries: Playground of Destruction that the player has a choice whether or not to kill.