I would say that it cannot be positively identified because what is very stressful to one person might be regarded as an exciting challenge to another. Some people excell and relish those sorts of jobs that keep them constantly on their toes - providing it doesn't go on for too long, others do not. Let me give you a few examples:
Working at a service counter when people are three and four deep crowding for your attention and you can only deal with one at a time; when things are going wrong; the telephone keeps ringing and you know that it's your duty to deal with each and every one of those persons and callers. This can be very stressful. Yet some people just get on with it.
Years ago I used to be an aeradio operator at a very busy airport, They used to call the position at aerground 'the hot seat.' I loved it. But after three hours we had to get off and take an easier job. Stress and adrenlaline levels can only be sustained for so long.
If you're a mother and you've got to cope with looking after a house full of babies and small children and you've still got to get the rest of your household duties done, the demands and stress can be very great. But, as I said, it is a matter of temperament. Some mothers breeze through this. Others do not.
So it really isn't possible to say with any real accuracy what the most stressful of jobs is.