Clutch screw one way for security.
Screw in but can not be screwed out.
Dynamite, lots of dynamite; that should shift it . . . or you could try T-cut?
coat the screw with vaseline and jam, leave to set for a few hours
Then add a teaspoon of nutmeg and leave for 2 hours, when you return the screw will have unscrewed itself.
But then it would be totally flat...... What good would that be unless he doesn't want to see it anymore ?
I'm on the assumption he wants to unscrew it. As was said above - Dremel a deeper recess across it's diameter to get a small flathead in there.