The Uruguayan brilliantly set up Liverpool's second goal in a 2-0 win, fighting to regain possession before laying the ball on a plate for Dominik Szoboszlai, who finished emphatically.
There was some doubt over the goal in the fourth minute of stoppage time, with Nunez putting in a heavy tackle on Jayden Bogle, but replays showed he clearly won the ball.
The home crowd still weren't happy with the decision, which was checked and cleared by VAR, and they expressed their anger.
However, the Liverpool forward was having none of it, and something in the crowd clearly caught his eye.
Facing the home fans at Bramall Lane, Nunez appeared to start blowing kisses to them, in yet another hilarious moment of his enigmatic career.
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Responding to the moment on X, one fan wrote: "One normal post-match reaction from Darwin, I will never ask," while another added: "Darwin is such a s***house."
Virgil van Dijk put Jurgen Klopp's side in front in the first half, with assist provider Trent Alexander-Arnold giving fans an unexpected eyeful moments before.