Machida

Machida was the chief antagonist of the Buffy episode "Reptile Boy" and was a snake-demon who masqueraded as a god in order to gain the services of the Delta Zeta Kappa, a society of frat students who believed sacrificing teenage girls to the snake "god" would give them wealth and power.

History
For generations Machida had been the patron "god" of the Delta Zeta Kappa society and rewarded his human minions with gifts of wealth and power in exchange for teenage girls to be sacrificed directly to him, unlike many worshipped demons he seemed to take part in the sacrifice personally as was the case when he rose from the depths to gaze upon Buffy and Cordellia: two girls that the society had picked for him.

Although Buffy was the Slayer Machida seemed either uncaring or ignorant of this fact and looked over his offerings, apparently pleased he opted on killing Cordellia first but Buffy had other plans and broke free - she fought Machida and ended his existence via slicing off his tail, following his death the Delta Zeta Kappa movement lost their patron "god".

Also many of the cultists who attended that night were arrested following the arrival of Willow, Giles, Xander and Angel - who fought them while Buffy and Cordellia were dealing with Machida.