Qetesh

Qetesh was a Goa'uld who once used Vala Mal Doran as a host.

Background information
Once an underling of Camulus, Qetesh ruled over at least one world, P8X-412, where she forced the inhabitants to mine the planet's sparse Naquadah deposits. When quotas were not met, she instituted both mass executions and mass torture. She has also been at war with Ba'al (although it is not stated precisely when) and killed, according to him, 10,000 of his best Jaffa. She also declared war on the Goa'uld Athena which waged a little while but they came together to find the Clava Thessara Infinitas. The Tok'ra eventually captured Qetesh, forcing the symbiote out of the body of Vala Mal Doran. She was likely killed immediately following the extraction. .

Alternate timeline

 * In an alternate timeline created when Ba'al changed the timeline so that Stargate Command or SG-1 never existed in the first place, Qetesh was his queen, having never been removed from Vala Mal Doran's body at all. But being suspicious of his knowledge of Earth, she conspired with Cronus to kill him and gain his power as her own. She learned about his time-travel device beforehand and she traveled to the planet where it was located, while her fleet bombarded Earth from orbit. 'Her Jaffa killed Dr. Daniel Jackson and Colonel Samantha Carter and mortally wounded Teal'c, but Colonel Cameron Mitchell had managed to escape through the Stargate into the past. Qetesh transported down to the planet containing the time-travel device but was killed by the wounded Teal'c when he detonated a grenade. The explosion killing her and also destroying the time-travel device. 

Behind the scenes
In the end credits for Stargate: Continuum, the name Qetesh is mistakenly mispelled as "Quetesh".