Everyone always brings up the moment of Ron standing on a broken leg, but no one talks about the moment before that one
But the force of its leap had carried it too far; it rolled off him. Dazed, feeling as though his ribs were broken, Harry tried to stand up; he could hear it growling as it skidded around for a new attack. Ron was on his feet. As the dog sprang back toward them he pushed Harry aside; the dog's jaws fastened instead around Ron's outstretched arm. Harry lunged forward, he seized a handful of the brute's hair, but it was dragging Ron away as easily as though he were a rag doll --
I find it poetic, we have one moment of Ron instinctively and without thought pushing Harry away when a huge black dog (That looks like the Grimm which is the omen of death) with a pulling strength enough to break a leg lunged, and then it's followed up by a moment of Ron deliberately choosing to stand to protect Harry in what was no longer a immediate split-second situation.