The Mechanic

An unnamed man (credited as "The Mechanic") is a member of the Solntsevskaya Bratva residing in Starling City, seemingly the bodyguard of the late Alexi Leonov.

Season 1
In "Lone Gunmen", When Oliver came asking for Alexi Leonov, the Mechanic believed him to be an enemy, and pointed a gun at him which resulted in Oliver almost breaking his hand. Oliver showed Alexi, along with the man, his Bratva star tattoo, revealing that he was a Bratva captain, and the man and Alexi apologized for disrespecting him.

In "Vertigo",

Season 1

 * Lone Gunmen
 * Vertigo