It has to be the Turks,

Those who stand in our way are punished...severely. The Turks are a violent organization, and Reno at one point tells them that they are "standing in the way"
Hardly ever caring about those we meet.They didn't seem to care about anyone else in Watui or Junon while drinking
Even though we were to take her back.Again, with Elena in Watui

The boss was killed.Tseng
Underground we see you at last.In the Midgar Sewers all three (Reno, Rude, and Elena fight you
Revenge is her purpose.Elena tries to punch you in Icicle Inn for "killing Tseng"
Killing is ours. Reno and Rude are the experienced killers
See you in hell.None of the Turks are exactly angels....

so yup, Ansem got it