His work is not so bad it could go down a 'poor performance' route, but his outlook creates a gloomy 'can't do' atmosphere. While I challenge (sometimes daily) his negative assertions - eg, about the quality of the work/performance of others or the chances of a project's success - I find it wearing and feel there must be a way of changing his work personality/behaviour for good. Any ideas?
It does you credit that you're still looking for a way of changing this doggedly tiresome person's attitude. A great many people in your position would have lost patience completely by now and - one way or another - engineered his unceremonious departure.
I suspect you suspect, as I do, that this may be a man who is deeply unhappy in a part of his private life and, in some sort of desperation, is taking it out on his work and his colleagues. It's even possible that he finds his own behaviour almost as maddening as the rest of you but is quite unable to do anything about it.
If this is the case, his problem may be so deep-seated that its solution is way beyond anyone but a member of his family or a professional therapist.
You seem to have tried as hard and as patiently as anyone could expect of you.
However, if you haven't already tried it, there's one further approach you might want to explore before giving up altogether.
By the sound of it, your attempts to get him to change his ways have so far all been fairly formal; so why not find out what a couple of hours in a pub can achieve? Buy him a drink, then put it to him as informally as you know how. Tell him his work is good enough; then ask him - as if you're baffled rather than critical - why he has to be so bloody miserable all the time. It's driving you mad, and a lot of other people, too. Tell him how much more he'd be liked and appreciated if only he could show a bit of light and optimism. Then buy him another drink and see if he opens up a bit.
If all this gets you nowhere, you can honestly tell yourself that you can do no more - and that your first responsibility is now to the rest of your team and the company: your curmudgeonly colleague will have to go. Tread carefully, of course. Don't take it all on your own shoulders: involve your own boss and your HR director, if you have one. If in doubt, consult The Penguin Guide to Employment Rights: The Essential Workplace Guide by Hina Belitz (Penguin, pounds 8.99).
Please address your problems to Jeremy Bullmore at: Management Today, 174 Hammersmith Road, London W6 7JP. Or e-mail: firstname.lastname@example.org Regrettably, no correspondence can be entered into.