Completing The Dexter Discordance will not
pop this achievement, so you'll have to complete The Meiko Incarnation
, which is really tricky during level 5. Don't even think about doing this escalation until you've reached Hokkaido mastery level 20, as it's impossible to do without using loadout items.
Level 5 is tricky because it combines the previous complication "Cascade" which requires that you kill the Hospital Director, Akira Nakamura, within 60 seconds of stealing the diamonds, with the "Ninja Biker" complication which requires you to kill both targets while wearing either the Ninja or Motorcyclist disguise, using only the katana, shuriken, or an accident kill.
This used to be a lot easier because you could knock out Nakamura in the main-floor bathroom and leave a breach charge + fire extinguiser near him, then detonate remotely after suiting up and stealing the diamonds. Now that fire extinguishers have been nerfed and only incur knockouts, a different strategy is required. Propane tanks work better than fire extinguishers, but there is no efficient way to get propane up into that bathroom without screwing up the timing or doing a lot of backtracking.
All credit for the video goes to Woopzilla. This run is from Hitman 2 so it accounts for all current conditions. Good luck!