Vegas trailed 4-0 after one period.
In their last meeting on November 5, Vegas won 2-1.
Vegas was once again blasted in the opening frame Thursday night at T-Mobile Arena, falling behind 4-0 to the last-place Los Angeles Kings after 20 minutes of hockey.
Toffoli scored his 12th goal of the season to make it 3-0, scooping up a puck off an Anze Kopitar faceoff in the left circle and then firing a wrist shot past Subban's glove side at the 18:44 mark.
TOP PERFORMERS: Max Pacioretty leads the Golden Knights with 45 points, scoring 20 goals and adding 25 assists.
The Golden Knights cut the lead in half with two second-period goals. It was also the third straight game in which the Golden Knights' opponent scored the first three goals of the game. Hornqvist followed a little over four minutes later when he slid a rebound of a Jack Johnson shot around Fleury and inside the right post for his 10th goal of the season.
The Kings "victory, coupled with the Ducks" defeat to Dallas, allowed the Kings to jump the Ducks out of the Western Conference basement. The Kings also received goals from two defensemen: Alec Martinez and Ben Hutton. Campbell went 2-1-0 for life against Vegas.
First period woes continued for the Golden Knights, who allowed the first goal for the sixth straight game. He improved to 5-6-4 in 17 games.
Smith brought Vegas back to within a goal with his 17th, chipping in a backhand feed from behind the net by Chandler Stephenson, but Jarry came up with several big saves down the stretch to deny Vegas' comeback hopes. Malcolm Subban made 18 saves and fell to 6-3-1 in his last 10.