I’m thinking that the conversation on the wall as the humans made their way away from Eden was a major formative moment for Crowley.
When Crowley says “You’re an angel, I don’t think you CAN do the wrong thing,” he is absolutely yanking Aziraphale’s chain. The book explicitly says it’s sarcasm and in the show, David Tennant’s delivery makes that clear with his smirk and sneery tone.
But when Aziraphale innocently takes the comment at face value, Crowley lets him think it was sincere. It’s his first act of kindness toward Aziraphale. My reading is that Crowley is happily surprised that an angel would allow himself to be comforted by his words and it takes away his desire to tease. He got his first little taste of doing good AND HE LIKED IT!
That interaction is perhaps the first time Crowley realized that he’s not necessarily cut out for sowing misery.
Also, consider his shock at Aziraphale’s admission.
Crowley was told to come to Eden and make trouble so he did. He doesn’t seem to have thought about it at all, just got an order and executed it. What if learning that Aziraphale has given his sword away is the thing that makes Crowley realize that he, too, can make his own unexpected decisions.
It was Crowley that gave free will to the humans, but maybe it was Aziraphale that made Crowley realize that he could also have free will. Even though Aziraphale hasn’t embraced his free will, he has perhaps just given Crowley the impetus he needed to do so.
And later, Crowley returned the favor when he explained about going along as much as you can. That was painful for Aziraphale but helped him to be more himself. It was a moment when he realized, like Crowley on the wall, that if doing good means breaking the rules sometimes, then sometimes that’s what must be done. In his guilt and fear, he didn’t put that together in Eden, but Crowley showed him at Uz.
Anyway, I’m rambling, but these two have made each other better, and happier, since the world existed and that’s just lovely.
