What is the most complete MS Word alternative?

The most complete is by far MS Office in a virtual machine: this is what I do.

If you will again be distributing those files you edited, it's pretty much necessary to use MS Office, because anything else can have unpredictable effects on the document.

If it is for your own use, OpenOffice (or LibreOffice or Go-oo, etc) is just about as good as MS Office and is the most feature-rich.

If you are in a KDE environment and the OO.o-derived products feel awkward or clumsy, then KOffice is an excellent alternative, although I find the .doc compatibility less-suitable.

If you require a minimal install size, Abiword is quite good. The online suites (Google Docs, Office Web Apps) are pretty good as well.