The programme aired last night, but several cast members told the Los Angeles Times that they thought it was too "subdued".
John Hensley, who played Matt McNamara, described the episode as "anti-climactic" and said: "I was craving for there to be some great twist. Those first two seasons, Nip/Tuck was quite successful at incorporating those.
"I was hoping to end on that note, and it just fizzles. It's a distinct choice [creator] Ryan [Murphy] has made, and I respect it. But I was so craving a twist."
He added that he felt "let down" when Matt ran away with Ava, saying that it was "not really explained".
Meanwhile, Kelly Carlson, who played Kimber Henry, explained that she liked the romance between Kimber and Christian but said: "I found myself reading the script and getting a little pissed off that my child was going with Ava. I was a little mad. I was a little upset. It made me sick."
Dylan Walsh, who has already said that he expected more from the finale, described it as "subdued" and admitted that he thought it was strange that his character Sean McNamara left to take care of a baby.
"I felt the finale should have been more about some closure with the things we'd already set up," he said. "It seemed like an odd thing to do."
However, several other cast members praised the final programme. Joely Richardson called it "mature" and an "absolute page-turner" while Julian McMahon said that it was "nice to be simple".
> Walsh already missing 'Nip/Tuck' co-star