I love this guy tbh, I have only fought it on regular new game but it was a fun fight. I just stayed under it closer to the back. If it starts moving at all dodge towards the back of it, you should be able to survive any of its attacks as long as you have decent fire resistance. If it flies to the other side of the bridge, just run underneath the bridge andnwait until it lands back on its starting position. I killed it at level 48 with Uchigatana +8 with a dex of 28, and it was honestly easy. Just run past it upon initial encounter and fight it after defeating the twin gargoyles and you should already be powerful enough. I don't know how hard it is on NG+ so I'll just trust people who say fire one shots. Also my dad said that it's possible to kill it if you have a lot of poison arrows and just hurt it faster than it heals, so that's also an option.