When Prime Minister Robert Fico of Slovakia returned to work this summer after recovering from gunshot wounds from a May assassination attempt, he released a video message titled “I forgive and I warn.”

Since then, there has been scant sign of forgiveness. But Mr. Fico has more than delivered on his warning to those he considers political enemies.

In recent weeks, he has presided over a rolling purge of anticorruption prosecutors, museum and theater directors, journalists and others he holds responsible for an atmosphere of “hatred and aggression” that he says led to the attack.

While his supporters cheer what they see as a long overdue cleansing of a system dominated by liberal elites, his critics see a vindictive, scattershot assault on people with little in common other than their shared role as perceived foes of Mr. Fico and his far-right allies in a coalition government.

The pace has been so rapid and its scope so wide that many in Bratislava, the liberal-leaning capital, are filled with foreboding that he wants to diminish the space for critical voices. Mr. Fico, they say, is taking Slovakia down the illiberal road charted by Viktor Orban, the authoritarian leader of neighboring Hungary, including by setting a course that is more antagonistic to the West and more friendly toward Russia.

“He really changed physically and psychologically after he was shot, and it is becoming really dangerous,” said Lubos Machaj, 70, a widely respected journalist who has known Mr. Fico for years and lost his job as director general of Slovakia’s state-funded public broadcaster in July.