Firstly, there are two tonics you'll want to make this easier.
Photographers Eye I - Located in Worley Winery's cellar in the Farmer's Market in a small shed, when you must gather the enzymes and water for the forest. Also can be bought at a Gathers Garden in Fort Frolic.
Photographers Eye II - Reward for reserving level 2 of the Rosie.
These will give you a combined boost of 25% in research.
Thuggish Splicers are plentiful in every level. They are melee attackers, usually using a pipe or wrench, so if you see a Splicer rushing you, they are likely a Thuggish Splicer.
They can be fully researched fairly quickly, probably before you even get the Photographers Eyes.
This achievement may not unlock after meeting the requirements, according to ICE Faux Pirate, I'm unsure of any way to force it to unlock, unfortunately.