Carl Soderberg tied the game 3-3 at 1:00 on the power play, Landeskog converted Rantanen's pass for his ninth goal and a 4-3 Colorado lead at 6:14, and MacKinnon scored his ninth at 8:38 to make it 5-3. Matt Nieto scored his second at 15:33 for the 6-3 final score.
"I love watching our team play like that," Avalanche coach Jared Bednar said. "The aggressiveness on our forecheck, hunting pucks down and staying on pucks, winning battles. Their reloads from the goal line to the tops of circles, the blue line and into the offensive zone, to turning pucks back.
"We were going to the net, there was a purpose. Ideally, you'd like to play like that 60 minutes every night but I don't know how feasible that is. But it's good to know that we have that in us."
The Landeskog-MacKinnon-Rantanen line combined for nine shots, three goals, seven assists and a plus-8 rating. MacKinnon is second in the NHL with 18 points.
"They're good," Duchene said. "They're all coming into their own. I look at a guy like Mikko and the steps he's taken, they're unbelievable. He was outstanding tonight. He made a lot of that stuff happen tonight in particular. They're good. I mean, that's a line you've got to contain. It's the age of super lines right now and that's one of them."
Ryan Dzingel scored, and Craig Anderson made 31 saves for the Senators (4-4-1).
Dzingel was parked just outside the right post when he scored his third goal at 2:42 of the first period to give Ottawa a 1-0 lead.
Duchene, shortly after a brief tribute to him was shown on the video board, scored his second goal at 10:27 for a 2-0 lead. Cody Ceci's shot from the point appeared to enter the net off Duchene.
"My favorite part, for me, was the tribute and the reception from the fans," Duchene said. "Meant a lot to me. I teared up. I had so much emotion going until midway through the second. It was a bit of a grind."
The Avalanche made it 2-1 when Samuel Girard, who was acquired from the Predators in the Duchene trade, scored from the slot at 10:20 of the second period. It was his first goal and the first by an Avalanche defenseman this season.
But Duchene scored his third goal 12 seconds later for to give the Senators a 3-1 lead.
The Avalanche cut it to 3-2 at 14:32 when Rantanen scored on a one-timer from the right circle off a MacKinnon pass during a power play.