World Cup History: Five instances when the tournament champion had a 100% win percentage 

#2 West Indies - 1979

West Indies maintained their 100% win record at the World Cups

Clive Llyod's men maintained their unbeaten record at the mega-event of world cricket with a memorable World Cup campaign in the year 1979. In the 2nd edition of the Cricket World Cup, West Indies were a part of Group B along with India, Sri Lanka and New Zealand. They won their first match against India by 9 wickets before their match against Sri Lanka was abandoned due to rain (the same problem existed in England 40 years ago as well!)

In their final group match, West Indies sealed the top spot with a 32-run win against New Zealand at Trent Bridge. In the semifinals, West Indies defeated Pakistan by 43 runs before winning their second World Cup trophy with a commanding victory over hosts England in the final.

West Indies lost their first ever World Cup match to India in a group match of the 1983 World Cup. Their next loss also came against the same opposition, when India overcame the Caribbeans in the World Cup final.