The tactics of Russian operatives have always been more nuanced than simply "eliminating the adversary". Typically, such extreme measures are reserved for traitors, like Sergei Skripal or the helicopter pilot who defected to Ukraine.

In certain instances, they opt for psychological warfare techniques, similar to those employed by the Stasi in East Germany during the 1970s and 1980s. https://en.wikipedia.org/wiki/Zersetzung

Guess where Putin was stationed in the '80s during his tenure as a KGB officer?