There is something in this:
Hive enhance the feelings of the inhumans he control.
Daisy told Coulson Ward kill people not because he feel nothing, but because he feel too much.
It was in the episode when the opened the portal to Maveth.

AIM financed Killian. It was not Killian.
AIM was the research branch of Hydra, initially.
Then got independant and produced a lot of interesting villains like MODOK

No one in the original gang die. But Buffy a couple of time.

Backups?
If he is digitalized, his brain can be copied and backed up.
Captain America you just erased copy 135 of version 2.1 of Arnim Zola brain.

"She is his thrall" is the correct way to tell it.
OR
"She is enthralled"

Because someone of them could kill or injure himself/herself. Because you have four very dangerous people in custody.
Because Lincoln and Daisy even more, are not just inhumans with cool powers, they have brain and skills.

It would explain why the crew on the planet behave like it did:
one killed himself jumping from a cliff, another burned himself and the last tried to kill Will the Astronaut and got axed.

We now know Hive infected can not spread the contagion.
Probably Hive need to spread the spores directly from himself and once they are inside the body of an Inhuman, they can not turn back to spores again.
probably they do not / can not reproduce inside the body of an inhuman, just go there and take control of the…

The simplest reason is, IMHO, different.

Or just put in a false recording of themselves

Amadeus Cho?

What May would do with ISIS?

As Reina predicted, "A day you could be monsters together"

The future is pretty readable by the hints we got:

He gave her a fair warning.

Thor did the same against Exitar "the Celestial planet killer".
2 km high celestial against puny Thor.
Thor had to manage against the Celestial immune system and destroy his hammer to just delay the being. Fortunately for him, the celestial had no bad feeling against him.

Exactly.
Stone of ???

The love triangle was resolved already when Will got killed.

He saw the man trying to crack Fitz head with a big rock. No explanation needed. Not after he shot him and he just keep going.

Not enough time to show a fight and everything else.