Rogue Xenomorph

In the comic Aliens - 

Rogue, a mad scientist, engineered the Rogue Xenomorph: a male designed as a weapon to rival the Queen caste, and thus help rid Earth of it's alien infestation.

The Rogue escaped and wreaked havoc until it was torn apart by a Queen.

In the book Aliens -

The Rogue was believed to be more powerful than the Queen.

Ernst Kleist, the scientist who engineered it, is shocked to find the Queen is in fact the superior specimen: The Rogue is larger and stronger, but the Queen's superior speed and intellect enable her to easily dodge the Rogue's brutish attacks, while she slowly wears it down and finally slaughters it. (Kleist is subsequently killed when he uses a sound cannon on the Queen until it goes critical, destroying the asteroid base he is on.)

The Rogue is seemingly much more aggressive, and mercilessly attacks smaller Xenomorph castes. Kleist finds the crushed corpses of the Queen's elite Praetorian guard.

Interestingly, the Rogue appears to have been engineered to ignore humans. When exposed to one, the Rogue examined him closely, but did not attack, and finally it ignored him completely. This may be due to the Rogue caste not having as strong a sense to use humans to breed as the Queen caste.