What a chapter for a return.
I can only imagine what Netero had to do to keep Beyond "under control", because even with whatever limitations he imposed on his son... he still was able to think, plan and operate what is a enormous operation to take control of a whole country, which the royal family has a very powerful and old nen spell running, and infiltrate not only a lot of people with a fanatical zealousness but create a a whole ass nen curse that anyone with a little sense would never try to do.
Beyond is using his own genetic parentage with those people as a catalyst for the curse, tying him with the control over the "keys" for the curse, but remember... nen is not a power of convenience, if one thing goes sideways if he screws up one detail of the conditions and restrictions... ALL of that putrid nen will go rushing back at him, even if he has a backup plan to protect himself (which I have no doubt he has), with such a massive undertaking... such a plan would not be a guarantee.
But now I fully understand why Netero tried to keep Beyond under control... this guy is dangerous, with all letters in capital, his ultimate goal is not just exploring the Dark Continent, he has other designs.