Here´s a guide from factor747 showing you how to get this achievement easy, without using the gas or dragging the targets around.
*Edit*
Did this achievement bug out on you? There might be a fix.
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Posted by ReptarOnIce3000
"
https://personal.hitman.io/For all those who are having issues and not getting the achievement, the link I have posted above will delete your Hitman server progress, giving you another shot! I did this and it worked perfectly! I just did the fall kill requirements, not even the coconuts, and it popped!
A few disclaimers however:
1. Account Deletion takes about a week. I submitted my account for deletion, and got an email about exactly one week later saying it was deleted.
2. This will wipe ALL progress. This means your level, all your challenges, escalations, EVERYTHING, will be gone. (When reattempting I would recommend also deleting your local save and NOT syncing to the cloud)
3. This not only deletes Hitman 1 data, but Hitman 2 as well, so save this for your LAST achievement if it didn't work for you. Also make sure you have finished Hitman 2 or have not started it yet.
Hope this helps! Finally finished this game after a year of nothing!"
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*Edit 2*
There might be an easier way to fix this now according to ShamelessHamish:
"BEFORE YOU DELETE YOUR ACCOUNT!!!!! Load into Bangkok, kill one of the targets and DIE. It unlocked immediately upon my death."
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Any feedback on this would be helpful to the comunity!