Well, as roundabout as it seems, so far as I know, permissions are positive-based and not negative-based. I'm a relative newbie and might be entirely wrong, but I don't know of a way to remove permissions from one specific user other than removing them, entirely, and then granting them to users you DO want to have them.
i want that the particular user cannot even browse the /tmp folder (where the permission by default are 1777)
so chmod o-rwx /tmp
More so (Remove read, write and execute permissions for generic users from everywhere else:
chmod o-rwx <everything else> ) doing this will make my many other process unworthy
I don't know what you mean by "unworthy", but it won't affect anything at all if you manage your groups properly. Add the users you want to have permissions in certain areas to the group that owns that directory/file, and the users shouldn't even notice the permissions change.
I agree that it seems like a pretty inelegant workaround jsut to lock out one user, but it will work and it will result in a more secure system overall.