The stirring “A Moment Like This,” the single Kelly Clarkson released upon winning American Idol’s first season, shows her pure vocal prowess. But her debut album, Thankful, also lets her flaunt her sassy, relatable personality on hooky, R&B-tinged pop. The cascading lament “Just Missed the Train” shows off Clarkson’s rich tone; “Miss Independent” takes on infatuation with jittery guitars; the languorous “Low” defiantly wears the wounds of a friend’s betrayal. Kicky and confident, Thankful is a pop triumph.