Three Nascent Soul Early Stage Thunder Cultivators, when facing regular Nascent Soul Middle Stage Practitioners, wouldn't necessarily all perish, and might even win while being weaker.
What he needed to do was find the Ten Thousand Beast Sect's core practitioner and kill them to avenge their sect's Thunder Cultivators.
Moreover, killing a core practitioner would be a significant blow to the Ten Thousand Beast Sect.
The number of core practitioners in any sect doesn't need to be many.
While disciples of Great Cultivators can directly become core practitioners, even Great Cultivators take on disciples in limited numbers.
In the Cultivation World, taking on disciples is a very cautious matter; the relationship between master and disciple is extremely close, even closer than that of father and son in the mortal world.
Cultivators place great importance on legacy, and disciples are the master's legacy.
