DISINFO: Neither the USSR nor the post-Soviet Russia has ever killed their opponents, so nobody can blame Moscow for poisoning the Skripals.
SUMMARY
During the last decades, neither Russia nor the Soviet Union has been engaged in extrajudicial killings; neither in the territory of Russia, nor abroad.
RESPONSE
Killing opponents of the regime was a practice familiar to the USSR, see e.g. the case of Leon Trotsky. There has also been a case of murdering a former Russian spy already - in 2006, Alexander Litvinenko was poisoned by two Russians in London. As the UK public inquiry has found, "the FSB operation to kill Mr Litvinenko was probably approved by [Nikolai] Patrushev [head of the security service in 2006] and also by President Putin”: https://www.theguardian.com/world/2016/jan/21/alexander-litvinenko-was-probably-murdered-on-personal-orders-of-putin