I think the best portrait photographers are extroverts. They need to be able to interact with the people they just met. They need to get the best results from their portrait subject. Their photos need to be interesting, colourful, contrasty, impactful. Their lighting needs to be interesting, they have to play with shadows, composition, depth of field.
I believe there is no professional portrait photographer without a good retoucher. There are things a photographer cannot control, like stray hair, acne, skin blemishes. Boosting the irises, skin softening, removing hot spots and much more will help to a portrait photography to be more appealing.