So you are using....different Queens from different movies? Ok.
Scar still had all his other weapons, and you conveniently missed out that the Queen had just come out of a mini-nuke explosion. Then the non-trained woman and Scar chained her to a water tower (which isn't here) and dropped her over a cliff (which isn't here).
The one Ripley fought, you conveniently missed that she used a powerlifter (that she was an expert in) and even then, did nothing to the queen.
The New Born was pretty big, and fought a genetically modified Alien Queen (i.e. it wasn't a purebred).
The Expendables don't carry anything more destructive than what the Colonial Marines and Predators carry. And the xenos can still beat them.
Meanwhile, these big beefy Expendables go into battle with exposed arms, no helmets, giant knives, tight little t-shirts....a drop of blood is going to phuck them up, those tails would skewer them like kebabs - and that's before we even have the psychological advantage the aliens have.
There is no sign of the Queen even being in close proximity to grenades when they exploded. It was used for the eggs. Comic feats dont count in movies.
The area is a factory, there is plenty of heavy equipment around.
Besides that, the Expendables have a nearly comic-like durability and skill of those of enhanced soldiers. Doesn't keep them from getting slashed, but it does make them more than simple marines as seen in Aliens.
It was in the same (small) room - having a whole belt of grenades in the same room didn't harm her significantly - all those eggs were birthed from her, after all, so it's not like she was in another room. I note you conveniently ignore the nuke that Scar let off.
Comic feats can count, using the same logic as what the franchise consultant of the Alien movies said:
It's literally his job for 20th Century. You're just lucky I didn't use video games, lol. Note how he says AvP is a completely different universe/franchise, and thus not canon to Alien - not that you were concerned about that.
There's plenty of heavy equipment around? So? They are also going to get a convenient trench to drop the queen into? They have access to a power lifter, something that future people don't even know how to operate (they needed Ripley who was specifically trained on them)?
Normal knives could stab them. They do not have comic-like durability against knives and hardcore acid, which is what the xenos are packing here.