- Edited
bachingchung If we consider that the MC is often a 14-30 year old young person who had the luck to find a cheat/super resource and became strong, it is quite possible for a sect of hundreds or even thousands to have a single person get lucky, too.... Or a team of them.... Or one of their heaven toppling, city destroying beauties catches an OP husband, who wants to unknot her "heart demon" by killing the MC. etcetc...
Maybe they will be scared, or maybe some super talent hides between the scrubs. We - as the readers - know that the MC will win at the end, but in the world itself only a dead enemy without loose ends is a good enemy(also he should drop all his treasures if possible).
There are no innocent bystanders in sects. The upper echelon uses and exploits, but also educates, protects and represents the other parts of the sect.
It's not even real genocide, if simply the whole sect gets killed. Genocide would imply you kill the whole race.