The 29-year-old put three fingers up to the home crowd to signify the amount of Premier League titles he's won since swapping Villa Park for the Etihad in 2021.
Grealish played the entirety of Saturday's match in the Midlands which saw Villa emerge as 2-1 winners over the reigning champions.
Villa's victory has seen Unai Emery's men leapfrog above Pep Guardiola's side into fifth spot.
The Citizens have now lost nine out of their last 12 matches in all competitions - more defeats than they have managed in the previous 106 games combined [eight].
And it was another performance to forget for ex-Villa skipper Grealish on his return to his former stomping ground.
READ MORE ON JACK GREALISH
Deeney: Grealish's legacy is in danger - he needs to leave Man City to feel the love again
Jack Grealish responds directly to Ant and Dec when asked about wild I'm A Celeb rumour
The England international has now gone over 365 days without a goal for City - a run spanning 45 fixtures.
Villa fans were quick to let Grealish know what they thought of his form as they mocked him during the early afternoon encounter.
During his Villa days, Grealish was often serenaded with chants of 'Super Jack' from the stands.
But those lyrics were changed to 'You're not super anymore'.
Most read in Football
Southampton confirm new manager but face anxious wait before Fulham match
'This is a crisis' - Man City stats from horror run are almost unfathomable
'Capitulation' - Frank Lampard taunted by fans as Coventry thrashed by Portsmouth
England World Cup winner who changed football forever dies aged 88
And it proved to be all too much for Grealish following the full-time whistle as he held up three fingers to highlight he was correct in his decision to join City for £100million.
However his gesture didn't go down well with social media, as one X user said: "Sooooo shamelesssss. He hasn't scored in years."
Another quipped: "Is that how many touches he has all game?"
A third added: "Wow Grealish doing that to the fans who once adored him! Shows how low a player can go!"
And this supporter joked: "He's showing us how many points we got today."
Meanwhile this fan then simply stated: "The 3 minutes he played in securing these titles?"
Grealish will have two more opportunities to get on the score sheet to avoid going goalless in 2024.
City host Everton on Boxing Day, before they travel to Leicester on December 29.