During the fight between Dumbledore and Voldemort (and Harry and Bellatrix) in the atrium at the Ministry of Magic in chapter 36 of Order of the Phoenix, Dumbledore uses various ploys to dodge, intercept, and otherwise not die from Voldemort’s Avada Kedavras.
Two of those involve animating the statue in the Fountain of Magical Brethren and letting the spells hit animated statues instead of Harry or Dumbledore themselves:
‘I have nothing more to say to you, Potter,’ he said quietly. ‘You have irked me too often, for too long. AVADA KEDAVRA!’
Harry had not even opened his mouth to resist; his mind was blank, his wand pointing uselessly at the floor.
But the headless golden statue of the wizard in the fountain had sprung alive, leaping from its plinth to land with a crash on the floor between Harry and Voldemort. The spell merely glanced off its chest as the statue flung out its arms to protect Harry.
Next second, he had reappeared behind Voldemort and waved his wand towards the remnants of the fountain. The other statues sprang to life […] and the one-armed centaur galloped at Voldemort, who vanished and reappeared beside the pool. The headless statue thrust Harry backwards, away from the fight, as Dumbledore advanced on Voldemort and the golden centaur cantered around them both. […]
Another jet of green light flew from behind the silver shield. This time it was the one-armed centaur, galloping in front of Dumbledore, that took the blast and shattered into a hundred pieces, but before the fragments had even hit the floor, Dumbledore had drawn back his wand and waved it as though brandishing a whip.
Both quotes from Order of the Phoenix, chapter 36: “The Only One He Ever Feared”; emphasis mine
So both statues get animated, both statues come between Voldemort’s Avada Kedavra spells and their targets—yet the spell glances off one statue and shatters the other into a hundred pieces.
Why did the statue of the centaur shatter when hit by the Avada Kedavra spell, when the statue of the wizard didn’t?
Note that the suggested dupe simply asks what Avada Kedavra does to inanimate objects, which evidently varies by what type of object we’re dealing with. This question asks specifically why two supposedly identical (except in shape) parts of the same stone statue/artwork react in different ways to each other right after each other.