My first lens was a 57/1.4. I used a Soligor 2X teleconverter which gave me, effectively, a 114/2.8. Getting close was not a problem but sharpness was not too good until at least f/8 (effective f/16). My next lens was a 28/2.8 and was not used for portraits. The next lens was a 135/2.8. It was a decent lens but only got down to about 5 feet. It was later traded in for a 135/3.2 which focused down to 3 feet. I found that adequate for tight portraits. Years later I got a Vivitar 135/2.8 Close Focusing lens. That lens goes down to 1:2 which is much too close for a portrait but I find it useful for anything from the near macro range to infinity and very good for portraits. I have this lens now in many mounts.
Over time I accumulated many other lenses suitable for portraits. My favorite may be the 100/2.5 Minolta MC Rokkor. I have taken nice portraits with the 85/1.8 Konica Hexanon, 85/1.8 Canon New FD, 85/1.8 Canon FL, 85/2 AI Nikkor, 100/2.8 Canon FD SSC/New FD, 105/2.8 Super Takumar, 100/2.8 Zuiko etc. They are all good and how far you want tp be from your subject when shooting really is a subjective thing. Medium telephoto macro lenses like the 90/2.5 Tamron or 90/2.5 Vivitar Series 1 are also good for portraits but can sometimes be a little too sharp. I find both older and newer 105/2.5 Nikkors good for portraits. There are times when I will try a portrait with a 200/2.8 Canon New FD or a 200/3 Vivitar Series 1. A lens in the 50mm range can work when shooting a small group of people or 2-3 people standing close to each other but I do not like its look for a tightly cropped photo of one person.