Russian assassin most highly paid police-informant

[professor rat]

Azef thus became both Russia's leading terrorist and most highly paid police informant. In that position he organized the assassination of Vyacheslav Plehve in 1904. Plehve, as minister of the interior, was Azef's nominal employer and the person who had ultimately authorised him to infiltrate the Socialist Revolutionary Party.

https://en.wikipedia.org/wiki/Yevno_Azef