There is currently a bug where these particular Mafioso don’t count towards the kill count. The Dev is aware of the issue and will rectify it.
How to Find Mafia Base (45 Mafia Kills)
So…
That does mean this guide is currently pretty useless, (sorry). I did however manage to unlock Yuri by driving laps around the road surrounding the central park area, then just targeting the mobster cars that spawned. It is quite a slow method and based on chance, but should be possible within 20 minutes.
Location
At the North East part of the map there is a building that overhands a cliff.
The building spawns the angry men in fedoras you need to kill to unlock the cosmonaut.
While you can take shots at them from the road, there’s a ramp to the East of the building that lets you drive around the other side, to get easier kills.
Yup they do not count, so instead just drive around the city and kill the cars. 1 car = 3 kills. Simple enough, also HOTDOGS !