  We report the results of an intense, spectroscopic survey of all 41
late-type, nitrogen-rich Wolf-Rayet (WR) stars in the Large Magellanic Cloud
(LMC) observable with ground-based telescopes. This survey concludes the
decade-long effort of the Montr\'eal Massive Star Group to monitor every known
WR star in the Magellanic Clouds except for the 6 crowded WNL stars in R136,
which will be discussed elsewhere. The focus of our survey was to monitor the
so-called WNL stars for radial-velocity (RV) variability in order to identify
the short- to intermediate-period ($P \la 200$ days) binaries among them. Our
results are in line with results of previous studies of other WR subtypes, and
show that the binary frequency among LMC WNL stars is statistically consistent
with that of WNL stars in the Milky Way. We have identified four previously
unknown binaries, bringing the total number of known WNL binaries in the LMC to
nine. Since it is very likely that none but one of the binaries are classical,
helium-burning WNL stars, but rather superluminous, hence extremely massive,
hydrogen-burning objects, our study has dramatically increased the number of
known binaries harbouring such objects, and thus paved the way to determine
their masses through model-independent, Keplerian orbits. It is expected that
some of the stars in our binaries will be among the most massive known. With
the binary status of each WR star now known, we also studied the photometric
and X-ray properties of our program stars using archival MACHO photometry as
well as Chandra and ROSAT data. We find that one of our presumably single WNL
stars is among the X-ray brightest WR sources known. We also identify a binary
candidate from its RV variability and X-ray luminosity which harbours the most
luminous WR star known in the Local Group.
