Complex sentence: Lee earned the nickname "Chunderella" from his stint on variety show "Family Outing", because the other cast members picked on him for being awkward and clumsy, particularly Kim Soo-ro (nicknamed "Stepmother Kim").
Split into simpler sentences: Lee earned the nickname "Chunderella (천데렐라)" from his stint on variety show "Family Outing". Everyone in the "family" would pick on him because of his clumsiness, especially Kim Soo-ro (nicknamed "Stepmother Kim").