Which character suffered the worst death?

[Immortan Jonesy]

I agree that the Ripley clone was f**ked up. She only knew suffering during her time.

I bet Dr. Shaw went through the same thing, except there was no one to put her out of her misery...

[OpenMaw]

Well, given the nature of David's rather confused behavior about Shaw... I mean when he knew she was preggers with black goo baby he did want to throw her into stasis. Granted he made a poor taste joke later on, but...

No, he seemed to care about her on some level, or at least have some affection. So for all we know he had her unconscious/semi-conscious/sedated in a Hannibal Lector type of situation. That's just what I'd prefer out of my psychotic villainous android. The kind of thing he did at the end of Covenant where he hushes uh... What's her name again? The one. Ya know. Survivor.

[BigDaddyJohn]

The unforgettable Daniels, common.

[The Cruentus]

I would say the AVP franchise is chock full of cruel and unusual deaths. the facehugger/chestburster is horrible and painful, but death comes quick. worse for those who are conscious throughout the process.
Acid can be painful death if it doesn't hit anywhere that would cause an immediate death.

Pathogen mutation such as Shaw's, though she was lucky to stop the process before it got worse.

If Predators skin victims "alive" then that is surely a nasty death.

[City Hunter Yautja]

Newborn, no question

Yeah that was disgusting scene and it made you pity it.