If I had a Ditto from the Fossil set as my active and my opponent had a Dark Sandslash as his/her active would it's Swift attack knock my ditto out, He/She Claims that Ditto's Transform is an Effect on Ditto there for Swift would Knock it out.
No. All Swift does is get to place it's full damage on the Defending Pokemon.
Things that affect how many HP the Defending Pokemon has are totally separate and still exist and are taken into account.
