Religion

Goa'uld
The Goa'uld enslave the people of planets they conquer and force the residents to worship them as gods. Depending on the people, the Goa'uld, and how long the Goa'uld stayed there, the people can continue to worship the Goa'uld as god long after he has gone or even died.

Origin
This is the religion of the Ori, a powerful and ascended race who convert everyone they can reach to Origin. If they cannot convert the population, they will kill them with various methods. As of Season 9 of Stargate SG-1, the Ori have started "moving in" to our galaxy by means of a supergate.