Danny Welbeck loves scoring against United - his header on Sunday was his third in four appearances against his former club.
Sold by Louis van Gaal in 2014 after 13 years at his boyhood club, Welbeck is now showing United what they're missing and proving a point.
When at United, Welbeck earned a reputation as the Reds 'big game' player and became highly valued by Sir Alex.
Best remembered for his performances in the 2013 Champions League tie with Real Madrid, his pace, work rate and intelligence often saw him utilised as a tireless winger to pin the opposition back.
Even though now he's a dangerous presence for a major rival, Welbeck remains loved and respected by many at Old Trafford.
Van Gaal sold him because he was not prolific enough so it's ironic that, since being shipped out, he's come back to haunt the Reds on three occasions.
Welbeck proved the Gunners match winner as he put paid to our hopes of silverware on his first return to Old Trafford.
His decisive goal knocked United out of the FA Cup at the last eight stage in the Dutchman's maiden season at the helm.
He was at it again in the next campaign, albeit in a losing cause this time as his predatory strike was not enough to prevent a 3-2 defeat (Welbeck notched Arsenal's opener).
That goal was overshadowed by Marcus Rashford's breathtaking brace as he launched his league career in style.
Welbeck took centre stage again on Sunday as he rose above Chris Smalling and Phil Jones to power home an unstoppable header.
His Arsenal career has been blighted by two career threatening knee-injuries, the latest of which ruled him out for nine months but he remains a vital part of Arsene Wenger's plans at the Emirates.
Jose Mourinho admitted that Welbeck, along with Angel Di Maria and Javier Hernandez, would not have been sold had he been in charge at the time.
It would be interesting to see where Welbeck - who boasts an impressive 14 goals in 34 games for England - would fit in now had he remained at the club.
Would Marcus Rashford have enjoyed the same rapid rise to fame that he has done with the presence of the Longsight lad in the squad?
Of course, Welbeck could have dovetailed alongside Rashford and Jesse Lingard in an all homegrown, entirely Mancunian front three.
But then we may not have needed to sign Henrikh Mkhitaryan and Zlatan and this season may have panned out very differently.