Following a 50-19 thrashing of the Wallabies in Auckland last week, New Zealand were equally dominant in crushing them 43-21 on Saturday.
Their devastating first-half in Sydney to take a 36-7 lead into the break was vintage All Blacks, with six tries in the bag to leave Australia shellshocked.
"That was excellent," said Rennie. "A lot of stuff that we did well last week, we were able to put 40 minutes of that together.
"Quality of the carry, winning races and brutality around the clean-out, and then quality of the decision making, the pass selection to put people in space. I thought we were really clinical.
"I'm proud of the character and the courage," he added. "But disappointed that we weren't as clinical (in the second half). I think if we'd scored a couple early, it would have really put the foot on the throat."
Two of New Zealand's tries came from rejuvenated fullback Beauden Barrett, who was largely overlooked during their recent "Rugby's Greatest Rivalry" series against South Africa.
Injuries opened the door again against Australia and the 147-Test veteran jumped at the chance, with Rennie full of praise.
"It just highlights how fortunate we are," he said. "Beauden's experience, communication, the quality of his decision-making is excellent. It's great having him in the mix."
The All Blacks went into the Sydney game with a slew of players out with injuries, including Ardie Savea, Leroy Carter, Caleb Clarke, Ruben Love, and Richie Mo'unga.
Knocks to Shannon Frizell and Samisoni Taukei'aho added to the casualty list ahead of travelling to Europe for the culmination of the Nations Championship next month.
Skipper Codie Taylor said he was proud of how the team bounced back after the South Africa disappointment.
"We had an honest look at ourselves after that RGR, and you know, as always, you're never satisfied and we probably walked away from that pretty gutted," he said.
"But also knowing that we were playing a brand of rugby that we could be really proud of and really grow on.
"To go and play in New Zealand and (win) the Bledisloe (Cup), and then a real mental challenge this week around owning the standards that we want to have in this team and step up. I thought we did that for majority of the game, so really proud of the lads."