I think it really depends on how many you have or how much damage they do
Eldar Space Marines Imperial Guard Dark Eldar Tau Chaos Space Marines Witch Hunters Gray knights Chaos Daemons Necrons Orks Tyranids
Space marines Chaos space marines Necrons Orks Tau Space wolves Daemon hunters Chaos daemons Eldar Grey Knights Tyranids Blood Angles Dark Angles Dark Eldar
I say tyranids But it depends how you play them?
Dawn of War featured the Space Marine, Chaos Space Marine. Orks and Eldar Armies. Follow Up Expansions Featured the Imperial Gaurd, Tau, Necrons and Dark Eldar. Dawn of War II Features the Space Marines, Orks, Eldar and Tyrannid Armies
The four species in Dawn of War II are the Space Marines, Orks, Eldar, and Tyranids.
Tyranids seem more fun with their biomorphs and such, but Eldar seem very cool, and elite. In the end the decision is if you want a horde of monsters (Tyranids), or a group of cool, calm and composed alien warriors (Eldar).
There is no best race in 40k but how you play and build it, but if i had to say the best of all i would say that space marines are the most flexable and are very hard to beat with simple armies like tau or dark eldar. if you like shooting llike me then tua or eldar are the best if you like combat then deamons,tyranids or orks are the best but over all space marines are the most loved and used.
AnswerImperial Guard Eldar and Tau Chaos, Necrons, Orks, Tyranids and Dark Eldar are considered the "bad guys".
Space Marines are the most popular faction, within the Space Marine faction the Ultramarine chapter are the most used as they are Games Workshops poster boys. After the Space Marines it would be Chaos Space Marines and Orcs then Imperial Guard especially after the release of their new codex. Tyranids will have a new codex in January so their popularity may rise and by far the least played faction would be the Dark Eldar, this is because they haven't had a new codex or and significant update since about 1998
In the original game, without expansion packs (Warhammer 40,000: Dawn of War), you have the option to play as the Orks, Space Marines, Chaos Space Marines, and Eldar. If you add the expansion pack "Winter Assault" (requires Warhammer 40,000: Dawn of War or one of its standalone expansion to play) then you gain access to the Imperial Guard. The standalone expansion, "Dark Crusade" (does not require Warhammer 40,000: Dawn of War, or Winter Assault to play, but you can only access armies which come with the game) 2 new armies, the Necrons and the Tau, are added. Finally, in "Soulstorm" (another standalone expansion which doesn't require Warhammer 40,000 or any of its expansions to play) adds the Dark Eldar army and the Sisters of Battle. Warhammer 40,000: Dawn of War is stand-alone. Its expansions, Dark Crusade and Soulstorm, are also standalone (Winter Assault is NOT standalone and requires the original Warhammer 40,000: Dawn of War game or one of its other expansions to play). However, you only get armies that you pay for. For example, buying only Dark Crusade and Soulstorm provides you with only the Necrons, Tau, Dark Eldar, and Sisters of Battle. You cannot access the Eldar, Space Marines, Orks, or Chaos Marines, who require Warhammer 40,000 original to play.
The main powers of the Eldar from the Warhammer video game series is their great physical mobility and psychic powers. They are able to live for thousands of years.
Answer-First there are the Imperial guard, the hammer of the emperor.-Space Marines, humanity's finest super humans-Chaos space marines, traitorous space marines who serve the chaos gods-Tau, the most technologically advanced weaklings, For the Greater Good!-Tyranids, bio-engineered monsters who want to eat all life!-Orks, Barbarian aliens with strong green bodies and an obsession with war-Chaos demons, vicious demons waiting to jump into this dimension and wreak utter havoc!-Necrons, ancient warriors souls inside robot skeletons, rising from the grave to reclaim their empire!-Eldar, mysterious raiders from a dying race, lighting fast and technology on the border of magic-Dark Eldar, Evil Eldar who seek revenge on the universe! they also perfected the art of torture - itch hunters and sister of battle