Cooper, who was born in New Zealand before moving across the Tasman, was roundly booed by the Kiwi public in every game of the tournament.
The 23-year-old was below par throughout Australia's run to the semi-final and was outplayed by Jonathan Sexton and Ronan O'Gara during the shock loss to Ireland.
To cap it all, Cooper suffered a significant injury in today's win over Wales as his World Cup came to a nightmare end.
Cooper damaged his anterior cruciate ligament in the 22nd minute of the third place play-off success in Eden Park, a setback that will keep him out of the game for at least six months.
But while Cooper now faces a lengthy recovery process, his halfback partner Genia has no doubt that the player who returns to action in time for the three-Test series with Wales in June will be a far more rounded star.
"It's obviously a change from all the booing," was Genia's assessment after Cooper was applauded from the field in Auckland.
"In terms of his character, he showed a lot. He showed a lot of guts and a lot of character. He'll be much better for it.
"Obviously the way he finished with that injury is disappointing, but he'll come away a better person."
As for the Wallabies as a whole, Genia was downbeat in his analysis of their tournament showing.
The Wallaby vice captain, who has been nominated for the IRB Player of the Year Award to be announced on Monday, described two defeats in seven games as a disappointment given the expectations the squad had prior to the start of the global gathering.
"Obviously we came here with the ambition to win and I guess in that sense we failed," added Genia.