What do u do if someone really smells so unclean it unbearable ?

Offer them some deodorant! Seriously, as a tutor I sometimes have this problem with students - there was one who was so wiffy the people sitting near him were almost gagging! As tutor, they expected me to do something about it. The best approach I found was to be quite up-beat a light hearted about it, 'blimey mate, a bit pongy today, have you been running a worked up a sweat? Tell you what, want to borrow a squirt of Lynx?' that sort of thing, seems to work better then taking them aside and getting all serious about it.