The Kahnkilla were a sentient arachnoid species of scorpion-like humanoids from the planet Kahnkakilijik, who started out as merciless conquerors and became a military force prevalent in the galaxy. They were one of the many species enslaved by the Rakatan Infinite Empire, and were used for Gladiatorial Combat, which they would excel in. This likely had an influence on their warlike culture and aggressive demeanor. Later they would be used by the Hutts as highwaymen and soldiers, and this would greatly impact their galactic reputation.
There was a common stereotype for them as thugs and mercenaries, which they didn't exactly oppose.