The [Monster Orb Release] was a skill of a monster where they release the full potential of their monster orb. This skill amplifies the strength of the monster several times and it doesn't have a side-effect on their body.
The difference between the third evolution monster and the second evolution was so wide. It was because of the [Monster Orb Release] skill. Souta's power was overwhelming for any second evolution monster but he always says that he couldn't subdue a third evolution alone.
Why?
Because of this skill... A cheat skill of the monster race that terrified the human and demi world.
Even though Souta's power reaches the realm of the B-rank, he still didn't have the confidence to go against the third evolution monster alone.
This was one of the reasons why humans and demis formed a party to subdue a single third evolution monster. The overwhelming power of the third evolution monster couldn't be compared to one or two B-rank adventurers.