All 7 soviet/russian nuclear submarines sunk in accidents, the most of any nation that operates this type of vessels, left to right, top to bottom:

K-27: The only Project 645 submarine (a variant of the Project 627 November class with liquid metal cooled reactors), it was irreparably damaged by a reactor accident (control rod failure) on May 24, 1968. 9 were killed in the reactor accident. After shutting down the reactor and sealing the compartment, the Soviet Navy scuttled it in shallow water (108 ft (33 m)) in the Kara Sea on September 6, 1982, contrary to the recommendation of the International Atomic Energy Agency (IAEA).

K-8: A Project 627 November class submarine was lost on April 11, 1970 while being towed in rough seas following a fire on board. The submarine was initially evacuated, but 52 reembarked for the towing operation. All hands on board were lost (52), while 73 crewmen survived on the rescue vessel. Location: Bay of Biscay, 490 kilometres (260 nmi) northwest of Spain in the North Atlantic Ocean.

K-219: A Project 667A Yankee I class sub was damaged by a missile explosion on October 3, 1986, then sank suddenly while being towed after all surviving crewmen had transferred off. 6 crew members were killed. Location: 950 kilometres (510 nmi) east of Bermuda in the North Atlantic Ocean.

K-278 Komsomolets: The only Mike-class sub built sank due to a raging fire April 7, 1989. All but 5 crewmen evacuated prior to sinking. 42 died, many from smoke inhalation and exposure to the cold waters of the Barents Sea. A total of 27 crew members survived.

Soviet submarine K-429: Sank twice, first in 23 June 1983 after a series of mistakes led to a catastrophic dive that eventually killed 16 men, latter raised, she then sank again in her moorings on 13 September 1985, where she was raised again and decommissioned. 

K-141 Kursk: The Oscar II class sub sank in the Barents Sea on August 12, 2000 after an explosion in the torpedo compartment. See Kursk submarine disaster. All 118 men on board were lost. All except the bow section was salvaged.

K-159: The hulk of the decommissioned Soviet-era November class submarine sank in the Barents Sea on August 28, 2003, when a storm ripped away the pontoons necessary to keep it afloat under tow. Nine men died in the accident.

Being a soviet/russian nuclear submariner has to be one of the most dangerous jobs in the world.