Kiddy League Coach

Kiddy League Coach is the true antagonist of the Buffy episode "Nightmares" despite him not appearing until near the end of the episode - his actions were directly responsible for the events of the episode: he is never named in the episode and is simply known as the Kiddy League Coach, he is the second evil Coach in Buffy canon (the other being the swim coach from "Go Fish").

History
The Kiddy League Coach beat a young boy under his care named Billy Palmer into a coma for losing a game and as a result Billy became trapped in an astral nightmare, trying to confront his fears - which manifested as the "Ugly Man", due to the Hellmouth's power Billy's dreams began to manifest into the real world and many of Sunnydale's residents became ensnared in their own living nightmares.

After confronting her own nightmares Buffy fought the "Ugly Man" and knocked him out, she then convinced Billy to face the monster - when Billy did so his nightmare ended and he miracolously awoke from the coma: as he awoke Sunnydale returned to relative normality (for Sunnydale anyway).

However as Billy awoke the Kiddy League Coach enters his ward, not suspecting Billy to be recovered, he instantly tries to flee when Buffy confronts him but is stopped by Giles and Xander before he is taken away by authories after Billy finally picked up the courage to inform them of what had happened.