When people get captured, they get dragged to some kind of portal. They transform into slaves and have one of their arms become claw-like or weapon-like. They are strong but not very fast.
They also seem to keep dragging stuff used as fuel by the aliens. There is some kind of sewer they drag stuff along.
The hero waits in line, is not recognized and purposefully transforms so he can destroy the portal. I do not recall the hero being a very good person, but in the end he does the right thing.
The Mutant Chronicles (2008) starring Thomas Jane, Ron Perlman, and John Malkovich.
28th century soldier Mitch Hunter leads a fight against an army of underworld Mutants.
I saw this movie on a hotel TV once and have occasionally searched the name I don’t know how many times!
The beginning of the summary on Wikipedia describes the machine changing people:
The plot revolves around a "machine" which came from space 10,000 years ago. The "machine" mutates people into barely intelligent killing drones, known as "mutants", that drag new victims to the machine for conversion.
