Avril Lavigne sang the song Complicated.
Avril Lavigne . Her breakthrough single , `` Complicated '' , peaked at number 1 in many countries around the world , as did the album Let Go . Lavigne has scored six number-one singles worldwide , including `` Complicated '' , `` Sk8er Boi '' , `` I 'm with You '' , `` My Happy Ending '' , `` Nobody 's Home '' , and `` Girlfriend '' . `` Complicated '' is the debut single by Canadian singer-songwriter Avril Lavigne , released in 2002 from her debut album , Let Go .