We all have revenge fantasies, but few of us ride our peeved daydreams to the top of the charts. This year we delegated that task to Alanis Morissette, a 21-year-old Canadian whose scorching single ''You Oughta Know'' turned an otherwise banal experience getting dumped into the banshee howl of a jilted goddess. Revenge is sweet. Not only did the song hurl her Jagged Little Pill toward platinum sales despite critical scorn (see 1995's worst albums, p. 130) it justified Madonna's Maverick Records and made it kinky to go to the theater. So who is Alanis? Black hair blurs her face on MTV. Her tunes flirt with cafe folk, raunch rock, hip-hop. ''I'm free but I'm focused,'' she sings. ''I'm green but I'm wise.'' At her core, she's a tough-gal belter from the old schoolPat Benatar for the age of anxiety, dishing out ''Hit Me With Your Best Shot'' with a very '90s splash of vengeance.