Subject: Just...
Author:
Posted on: 2019-07-15 11:05:00 UTC
...lure them to a airlock, shut the door on them, and vent them into space.
Or...
...deliberately decompress the entire module they're in, by sabotaging the nearest airlock and sealing all the hatches.
Or...
Drill a hole in their spacesuit, or weaken a stress point significantly. While they're in a pressurised environment, the suit won't pop. However, if they're on a spacewalk, and you've put the weak point near a joint...well, they're screwed.
Hell, you could even just club them with a sufficiently blunt object, then drag the body to a airlock, and vent them into space.
Then there's the joys of poisoning with a lethal dose of painkiller (though I doubt contemporary space agencies provide stations like the ISS with enough dosage of painkiller to deliver a lethal dose), sabotaging their EVA pack to thrust them into deep space, sabotaging the oxygen supply in their suit, or just gourging out tbeir eyes with a fork, shoving the said eyeballs in their mouth, forcing them to swallow, and then stabbing them in the gut until their die.
Murder is fun!