This is a very hard challenge but i will walk you through it. I got this Trophy on Lady Boyle’s Last Party.
1. Once Samuel let’s you off the boat. Head right and into the alleyway/building without being seen (in my testing, if you are seen, the amount of Weepers that Spawn are less for some reason. No idea why but they do.)
1.1 Once you are in the building, get the attention of the nearby Weepers and go back out the way we came.
2. Get the attention of the nearby Guard and try to get him and the Weepers as close as possible. Once you are ready, Freeze Time and use everything you got. If you plan on using SpringRazors, don’t put them directly on the Weepers. They will diminish in damage compared to when placed directly on the ground.