The convicted Russian killer bounded off a plane in Moscow on Thursday, hours after Germany freed him in a wide-ranging prison exchange with Russia. President Vladimir V. Putin hugged him on the tarmac, in a hero’s welcome.

Zurab Khangoshvili, the brother of the Chechen exile shot by the assassin, repeatedly scrolled through the video of the scene, watching from his home in Germany with profound sadness, he said.

“It squeezed my heart,” he said, as he thought about his dead brother. No German authorities gave the family advance notice, he said. “That man killed someone here, and then he went back to Russia to a welcoming ceremony with this huge red carpet. It was unfair.”

Germany played a critical role in the complicated trade that on Thursday secured the release of 16 prisoners to the West in exchange for eight prisoners to Russia. No part of that deal was more fraught than agreeing to release Vadim Krasikov, sentenced to life in prison in 2021 for killing Zelimkhan Khangoshvili, a Chechen separatist commander who had sought asylum in Germany.

If the German government initially balked at the idea of releasing Mr. Krasikov, the main quest for the Kremlin, Chancellor Olaf Scholz eventually overcame the opposition within his government to champion it.

The question now is how the aftermath will play out in Germany. On the one hand, the release violated the longstanding German practice that politicians not meddle in court decisions. Yet criticism thus far has been muted, not least because the most vocal critics of the chancellor’s foreign policy all achieved something they wanted, analysts said, be it engaging with Moscow or the moral victory of releasing democracy activists from prison.