The opposition activist convicted of treason has long rankled the Kremlin.

Even before he was sentenced on Monday to 25 years in a Russian penal colony, Vladimir Kara-Murza considered himself an enemy of the Kremlin.

The Russian opposition activist and Washington Post contributor was born into a family of acclaimed journalists, scientists and lawyers. Two of Mr. Kara-Murza’s great-grandfathers were executed as spies and “enemies of the people” during Stalin’s great purges, according to Meduza, a Russian news website. His grandfather was arrested in 1937 and served a sentence in labor camps in Russia’s Far East.

Mr. Kara-Murza’s activism long rankled Russia’s political elite. For a time, he acted as the federal coordinator of Open Russia, a civic group founded by Mikhail B. Khodorkovsky, the former chief of Yukos Oil and critic of President Vladimir V. Putin who served years in prison in Russia.

Mr. Kara-Murza became known as a vocal critic of what he called a Kremlin policy of assassinating political enemies. He also drew the Kremlin’s ire when he lobbied for the use of Western sanctions to punish Russian government officials engaged in human-rights abuses. He urged American lawmakers to expand economic sanctions against the Russian government under a landmark law known as the Magnitsky Act that was enacted by Congress in 2012 and expanded in 2016.

Sergei Podoprigorov, the judge that delivered the sentence on Monday, was one of the Russian officials sanctioned by the Magnitsky Act.

Mr. Kara-Murza survived what he characterized several years ago as two government attempts to poison him — both of which sent him into a coma.

When President Vladimir V. Putin ordered the full-scale invasion of Ukraine in February 2022, Mr. Kara-Murza went on to strongly criticize the move in speeches in the United States and Europe. Despite warnings that he might be at risk, he continued to travel to Russia and work there.

In April, Mr. Kara-Murza gave an interview to CNN from Moscow in which he criticized the Kremlin for the war in Ukraine, calling Mr. Putin’s rule “a regime of murderers.”

He was picked up and detained hours later.