After betraying his old friends, and betraying Harry, he betrayed Lord Voldemort with just a flicker of hesitation when he tried to kill Harry in the cellar of Malfoy Manor.
Whether intentional or not, that hesitation caused his hand to turn on him, and Wormtail ended up strangling himself.
He was a rat who clung to power, and while he was crucial to Lord Voldemort’s return, I doubt Voldemort missed him, or even cared all that much that he was gone.
Peter Pettigrew was a worm, who got what he had coming to him.