Alt-rock upstart Avril Lavigne came crashing into the charts in 2002 with a sound that stuck two black nail-varnished fingers up at the hyper-polished world of classmates Britney Spears and Christina Aguilera. From the chugging, three-chord pop-punk of “Sk8er Boi” and “My Happy Ending” to the country-hued, catchy melody of “Complicated” and the twinkling balladry of “I'm With You”, the Canadian singer proved herself a crossover star, garnering legions of both mainstream and fringe fans with her Cali punk-indebted sound. In later years, she grew into a more mature pop sound with less of a rock edge, as heard on the touching ballad "Head Above Water," which addresses her battle with Lyme disease.