If I have a unit that says ignore deflect, and enemy has deflect 2, do I ignore all deflect or do I still have to pay 1 power?

You ignore all of it — you pay 0 extra Power.

When a card says "Ignore [Deflect]", it treats the Deflect keyword as Inactive for that spell/ability's cost calculation (Rules 720–721). Inactive abilities do not apply at all. So Deflect 2, Deflect 1, Deflect 5 — none of it adds cost. You pay nothing extra for targeting that unit.