I’ll take this to mean in the sense if you were in the direct middle of playing it and you stopped, I’d say Octopath Traveler II due to the chapter structure and strictly turned based combat is easier to pick back up. Personally it isn’t too hard to get back into Xenoblade either for the combat since it is deceptively more simple than it looks on the gameplay front, but you’d want to stop at an obvious break point in the story if you dropped it. FFXVI I’d say is the most difficult. The battle system isn’t super complicated, but it definitely has a unique rhythm to it all the same. Took me about an hour to get comfortable with it again between beating it at launch and playing the DLC five months later.