I haven't kept up with JAV, especially after ScanLover died. But two older girls fit this thread.
First is Sora Aoi. I thought she was the most overrated actress in JAV. Her movies were lame. She barely got fucked, often doing BJs, handjobs and tit fucks. Most of her older movies would have maybe 2 of 5 scenes with actual fucking. One of her S1 movies ran a full hour before she got fucked for the first time. Meanwhile Acky and Yuma were doing sex in every scene. She was dating that fat ugly guy at the time and put in no effort. Then they broke up and starting with SOE-183, the Fluid Exchange movie, she amped it way up. Suddenly she was getting fucked in every scene. She did 2-3 guys at a time, which she never did before. She did scenes that ran 30 minutes, full of energetic fucking. She really ended better than she started.
The other was Mihiro. She was one of the last big fakers, using the mosaic to hide that she wasn't being penetrated. It was a big joke on SLF. Then she signed with S1 and suddenly started getting penetrated, and in a big way. She was doing movies with 7-8 scenes, lots of wild fucking, facials, you name it. She really turned it on. I just had a hard time getting past that nasty pussy of hers. She had a really thick, hairy bush and her pussy lips looked black, almost necrotic. Good thing she had a cute face.