Complex sentence: He won the WBC light heavyweight title in 1978 from Miguel Angel Cuello and then lost it by defeat to Marvin Johnson with a 10th-round KO in Italy (December 2,1978).
Split into simpler sentences: He won the WBC light heavyweight title in 1978. He lost the WBC light heavyweight version title by defeat from Marvin Johnson with a 10th-round KO in Italy (December 2,1978).