Sorry but I'm a newbie and just need to be clear that activating Vader's ability is a guaranteed hit. Meaning if my attack yielded 1 hit and the defender rolls 2 evades they can't use the second evade to stop Vader's active ability. Is this correct? Thanks for the help!

you can deal no damage with your initial attack, then vader (costing you two health off the ship) then deal one damage. If you have gunner on that ship as well (or a gunner effect) you can repeat the attack and hit or miss again use vader's ability to deal a damage

After your attack is resolved Vader triggers. So in your example the defender would suffer no damage after the attack, you then declare the use of Vader and suffer 2 damage on that ship to simply deal a critical damage to the enemy. It is completely unavoidable as long as you perform an attack first.

Remember Vader doesn't ignore shields since he deals a critical damage and not a face-up card.

Yes I know a ship with shields would only lose a shield. Thanks for the replies