A known professional photographer here in Miami, a good friend for many years, asked my opinion about the 85 mm f1.8 Nikon lens. He told me he was interested in improving his portraits and needed a good portrait lens. I know he owns a Nikon two touch 80-200 f2.8 and I asked him if there was something wrong with his lens. He said no.
I cannot understand why you need a “better” lens for portraits having the excellent 80-200 f2.8 was my reply. Perhaps you meant portability? No was his answer. He was after a “better” lens for portraits and portability was not his priority.

I am no professional photographer although years ago I made a part time living as a professional. My portrait lens of preference has always been the Nikon 105 mm f2.5 and mine is from 1969, single coated, a lens that has served me well and continues to do so.
Perhaps I do not have the right answer but my feelings are that the best lens for portraits is the lens that you happen to have in your camera when you are shooting. Even a wide angle with its distortions of facial features could be exactly what you want. I do not know of your expertise as a photographer and I do not know what your artistic style is.

I asked this young man to pose for me. It is an indoor shot with the model looking into a window facing south. The lens I had in my Olympus OM-10 Mk II was the 40-150 f4-5.6 kit lens. I have the 12-40 f2.8 Pro, a better lens and a Sigma 60mm f2.8 Art which is a very sharp lens for micro fourth thirds but it was the 40-150 lens what I had in my camera. I simply set it at 100 mm and opened it up to its maximum opening. I could be too old and too lazy by now but I though the kit lens could do a good job. I went with ISO 400.

Technically there are some things I could have done for a better portrait like selecting a better lens. I could have used a reflector to bring more light into the shadow areas although I like it like it is. Even a low intensity hair light could have been effective but available light was all I had in mind. I did not pose him and let the young man to show his spontaneity.

I tend to warm a little bit my b&w images to simulate the Agfa warm tone fiber base paper I used in the past. I kept sharpening to the lowest setting. I like to add contrast to my b&w images. Original RAW data edited with Olympus Workspace and Affinity Photo.
Which lens for portraits? A dedicated portrait lens between 85-135 mm is an excellent choice but if you do not have the budget use good techniques and the lens you have now in your camera. You could be pleasantly surprised at the results.

Linda, the focal length of the lens determines the position of the camera to the subject to fill the frame appropriately. The longer focal lengths will place the camera further away from the subject but still produce the same size image on the film or sensor. Thus, someone who is familiar with me will not feel uncomfortable with the camera, and me, closer. For that, I'd use the 85mm lens. For someone who is unacquainted with me, I'd use the 135mm lens and place my self and the camera a bit further from the subject.

Providing a reasonable comfort zone for the subject allows for a more comfortable environment and a more natural-appearing portrait.
--Bob