So I've searched ever where for this answer but I guess I'm missing something. Can I use a Vaders crew card ability if I'm stressed? The reason for the confusion more or less has to do with the definition of an action. As the card does not say action anywhere or free action but specifically refers to an attack. Can you perform this card when stressed?

if a particular ability is an action, the card text will start with the Action: header

So I've searched ever where for this answer but I guess I'm missing something. Can I use a Vaders crew card ability if I'm stressed? The reason for the confusion more or less has to do with the definition of an action. As the card does not say action anywhere or free action but specifically refers to an attack. Can you perform this card when stressed?

Cards only do what they say, and importantly, DON'T do what they don't say. Vader says nothing about stress, nor about being an action (which would make it impossible if you were stressed) it only says 'after you make an attack', so that's when it happens.

Don't assume stuff that isn't written on the card, generally. If it's an action, or it's blocked by stress, it will say so.