Razzaq scored a quick fire 34 and took three wickets as Pakistan recovered after losing the series 2-1.
"He's a match winner, I've always seen him as one," Afridi said. "In the past there have been some games where victory looked unlikely, but he was able to see us through."
New Zealand will go into next week's Test series on a relatively high note after they ended their 12-match losing streak in the shorter format with a victory in the first T20 of the series.
New Zealand captain Ross Taylor felt that a win in the final T20 would have been a good boost, but Pakistan had bowled well.
“We wanted to go out and win series 3-0 after what's happened over last few months but Pakistan bowled really well too. We were looking forward to a good start given how they started, but the way Razzaq and Afridi bowled it was just outstanding," he said.
The teams will next play two Test matches in January, followed by six one-day internationals.
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