CARDIFF, Wales — Cristiano Ronaldo capped his greatest year by helping Real Madrid become the first European champion to retain its title since 1990, showcasing his enduring lethal scoring qualities Saturday night in a 4-1 victory against Juventus.

Ronaldo scored twice to become the first player in the modern era to score in three finals.

Having won the title once with Manchester United, Ronaldo has done it three times in four seasons with Madrid. It’s the latest victory in an incredible 12 months for the world player of the year.

It began with Ronaldo winning his first title with Portugal at the European Championship. Then came the Club World Cup with Real Madrid, then the end of a five-year Spanish title drought.

Ronaldo’s first strike at Millennium Stadium was canceled out by Mario Mandzukic’s exquisite 27th-minute hook shot. It was the only high point for Juventus on a night when the Italian champion was outclassed in its quest for a first European title in 21 years.

Madrid’s supremacy was clear in the second half.

After Casemiro put the Spanish champion back in front in the 61st minute, Ronaldo turned in his 600th career goal at the near post three minutes later, and Marco Asensio wrapped up a record-extending 12th title in the 90th.

“In the second half, Real Madrid pushed the accelerator,” Juventus Coach Massimiliano Allegri said, “and we remained too static and sat back too long.”

Madrid’s attacking brilliance proved just too hard for Juventus to contain as Zinedine Zidane won his second Champions League title in 18 months as coach.

“Zidane believes in us a lot,” Ronaldo said. “He knows that we are a very good team and that’s why we proved it in the second half.”

No team since AC Milan in 1989 and 1990, when the tournament was a knockout competition known as the European Cup, had won back-to-back titles.

Real Madrid won the first five European championships, from 1956-60, and holds the overall lead with 12 titles. AC Milan is second with seven but hasn’t won since 2007. Tied with five titles each are Bayern Munich, Barcelona and Liverpool.

The victory was a blow to Gianluigi Buffon, the 39-year-old Juventus goalkeeper who has won virtually every other title, including the World Cup.

“(Madrid) showed their class and the attitude needed to play in this kind of game,” Buffon said after losing a third final.