Board Thread:Warhammer 40k General Discussion/@comment-46.162.84.254-20130704080553/@comment-6078851-20140712021347

granted it would be a colossul showdown, but even if the necrons were to win there's a good (probable) chance that they would be mortally wounded (as a species) afterwards, and a concentrated campaign involving an astartes and eldar alliance could potentially cleanse the galaxy of the remaining necrons. that's if it was only the necrons fighting against the tyranids, but as i see it, it would take an alliance of most of the major races to win against the tyranids.

but as you say it's very debatable, hence why this thread is getting so long :)