Kadri scored on a rebound near the right post after Marc-Andre Fleury made a save on Joonas Donskoi.
"First and foremost, just try to win the face-off," Kadri said. "We just tried to keep it simple. [We] told the [defensemen] to get the puck and we just hopped on the rebound."
Nathan MacKinnon and Brandon Saad scored, and Philipp Grubauer made 27 saves for the Avalanche (8-4-1) in their first win since they had five games postponed due to the NHL COVID-19 protocol. Colorado lost to Vegas 1-0 in its return here Sunday.
"I thought they were way better and we were better too," Avalanche coach Jared Bednar said. "It was a competitive game. Under the circumstances for our team, finding a way to carve out a win in regulation was exceptional."
Max Pacioretty and Jonathan Marchessault scored, and William Karlsson had two assists for the Golden Knights (10-3-1). Fleury made 22 saves.
"I really liked our effort tonight. Three games in four nights," Vegas coach Peter DeBoer said. "I liked that the second and third periods were our best periods. I think the guys dug deep and pushed through."
MacKinnon scored on a one-timer off a pass from Mikko Rantanen at 7:08 of the first period to give Colorado a 1-0 lead. It was MacKinnon's third goal of the season and first since Jan. 21.
The Avalanche were 0-for-3 on the power play in the first period.