"Surgeyev, Kudrenko's right hand." "You know these bastards personally, eh?" "We go back aways."
Sergeyev was second in the command of Kudrenko's Spetsnaz group. He was a major antagonist of Syphon Filter: Logan's Shadow.
When Logan was in a mission in Georgia, he killed Sergeyev predecessor, Maksim Lebedev, and seriously wounding Sergei Kudrenko, leaving burns over fifty percent of Kudrenko's body. Sergeyev assumed command of the Spetsnaz and rebuilt the company as Kudrenko recovered of his wounds .
Syphon Filter Logan's Shadow
Sergeyev, a member of the Russian Spetsnaz, was the primary assistant to commander Sergei Kudrenko after the death of his predecessor, Maksim Lebedev. He had died as part of a failed double-assassination where Gabe Logan targeted him and Kudrenko but only killed the former, while the latter was severely burnt. Sergeyev assumed command until his leader healed, and from then he remained loyal. Kudrenko sent him to direct a salvage operation for the X-Z-2, but Logan was there to kill him before the Spetsnaz escaped.
You fight him inside the reactor chamber. Watch out - he stands in front of glass panels, and a wild shot on your part will breach the nuclear core...potentially detonating the device.
Since he's armed with a machine gun and can shred you especially on higher difficulty modes, your best bet against him is an explosive dart. This will kill him immediately. Otherwise, a sniper shot to his oxygen tank is necessary.
Be aware that killing him will unlock the third hidden evidence for this level.