Comments posted to our Bloodborne Wiki
A useful tip I found for fighting this bich is to lure him onto one of the flat platforms with the statues of amygdala on them, when he is there he can get stuck and doesnt tend to attack if you keep the corner of the Flat platforms in between you. Once this is done, you can keep power hitting him, and he will almost never attack back
My best method is to stay far away and wait for him to run at me while his Chikage is non-transformed, then ripost him the moment he's about to stab, preferably with a pistol as opposed to the Blunderbuss or Ludwig's Rifle. Works 95% of the time, offering an easy visceral, followed up by a long enough window for a charge attack, but it might take some time figuring out the right time to fire.

Get away another 3-5 backsteps, avoiding his quickstep-southpaw patterns and numbing mists, rinse, and repeat. He may or may not use a blood vial at some point, but you probably won't need more than 20 bullets to finish him off. When he transforms his weapon, he does become more predictable, but don't get too ****. Let his health drain on its own, if you must. Above all, don't forget to equip gear with great Blood DEF, like the Cainhurst Armor or the Knight's Garb, or better yet Maria's Hunter Garb if you have it. These sets also have pretty good Thrust resistance. Most often, you'll probably be dying to his Repeating Pistol, though, because of course he has unlimited bullets.
The best way to kill him (non legitly) is by taking him out of his Agro range which is the outside of the cathedral you can get him trapped behind the door and hit him with power attacks
I found that luring him to the stairs and throwing poison knives at him as his AI resets him back to his spawn location to be the easiest way to cheese him. But once you're good enough at the game, few fights are as exhilarating and challenging as having a straight-up fight with this guy. Even after playing 1500+ hours of Bloodborne, this hunter is still harder than most bosses.

If you really want to test your skill as a Bloodborne player, fighting the Bloody Crow of Cainhurst without exploiting him is definitely a worthy challenge.
Using the untransformed ludwigs sword and just spamming uncharged heavy is a good way to kill him because he will always get staggered by it. The stab also tracks his rolls and most of the time he just runs into it. The hardest part is avoiding his gunfire.
Hunter Boss Fights: Good!