Lambert was in a worse situation. She was weak, unarmed and had no idea where the creature was or where it might come from. She had no truly well armed protectors. No group of marines, no dropships or promise of search party.
Its easy to be afraid under those circumstances.
Hudson had weapons, auto turrets, motion trackers, comrades, vehicles, and military training/experience. He even had the information from Ripley ahead of time, the physical strength of a grown man, a good synthetic, capable superior officer and a gameplan. And with all this he was still losing his sh!t.
Was it cowardice? Probably. But to be afraid with all that manpower and equipment on your side must've meant he was legitimately scared to death.
Purvis. Maybe not character on its own but the idea he represents: average dude kidnapped and implanted with lethal Alien creature. Can you just imagine being in situation like that? It's really terrifying knowing that's something like this can happen to anyone and anywhen.
Also: "What's in-f**king-side me!". I love that line so much. I think i would say smth similair to this in such case.
For me it's Lambert. Her death has always been intriguingly brutal and memorbale. Her character who was always so sobby and full of emotion was someone who I felt like represented the audiences fear pretty well. Hudson is a close contender, Purvis wasn't half that bad either.