No question - Novell
They were so cocky and confident because of their enormous install base, that they neglected to implement a true multitasking, multiuser OS - of course NT was/is not multi-user - so with the aquisition of UNIX and morphing of it to UnixWare, we all thought this problem was going to be fixed, with UNIX in the back running apps and databases, and NetWare up front for file/print/LAN. It never happened. They did NOTHING, not with OS/2, not with UNIX, NOTHING. Those idiots could not even come up with a 32bit client that worked and was easy to install. They were still in the world of packet drivers and DOSware in the mid 90s.
The stupidity and venality of Novell is the direct cause of Billy's overwhelming success. IBM can be faulted as well, but that is mainly a marketing issue, not active stupidity. OS/2 was a fine product that received no overall backing from Akers and friends.
-drl