0 Stress: Four arms that work independently. Sense infared light.

1 Stress: Use your enhanced muscles to lift a thug one-handed. Hear a conversation across the room. Eat something typically nonedible. Track a creature by scent.

2 Stress: Ripping chains apart through sheer strength.

Some of these are examples from the book, but in the case of 'ripping chains apart through sheer strength,' that idea can carry over to other things than chains.

I also want to suggest a possible third option: take the default Playbook ability and explain how your Xeno race accomplishes that in a different way than a typical character might. For instance, we have a Muscle that's basically a Trandoshan from Star Wars and he's using natural strength/scaly armor to explain the Starting Muscle ability in the lieu of Xeno abilities.