Which crocodile is the largest in the world?

Unfortunately, there is no definitive answer as to which crocodile is the largest in the world.

This is primarily due to the fact that there is doubt about the sincerity of the data from the various sources.

Below you can read the explanations from resp. Guinness Book of Records and Wikipedia.

Guinness Book of Records
Guinness Book of Records is considered one of the most serious sources when it comes to world records, but when it comes to which crocodile is the world's largest, there seems to be a bit of data missing in their record - Guinness Book of Records writes the following:

Cassius, an Australian Saltwater Crocodile, is the world's largest captive crocodile and is 5.48 m long. The Australian saltwater crocodile is the largest and most fearsome of today's species. Some individuals can live more than 100 years, grow up to 7 m long and weigh more than 1 ton (1.1 ton)!

Wikipedia
According to Wikipedia, the world's largest crocodile is called Yai (which very literally means "big" in Thai) and is 6 m long and weighs 1114.27 kg. Yai was born on June 10, 1972 at the famous Samutprakarn Crocodile Farm and Zoo in Thailand. Yai also holds the record for being the largest crocodile ever captured.

The world's longest crocodile caught alive is called Lolong and measures 6,069 m. The crocodile was captured by a team of scientists working for National Geographic in Agusan del Sur Province in the Philippines.

However, some naturalists believe that the longest crocodile ever killed by man was a 7 m long crocodile that was allegedly shot in Dhamara, India in 1926. However, the targets for this crocodile are based solely on estimates based on the skull of the crocodile (the skull makes up 1/9 of the total body length of this crocodile species - and one can thus estimate its size with some precision).

Conclusion
The conclusion is that there can be no official record holder for the title of the world's largest crocodile when the data on which the measurements are based are inaccurate.

Which crocodile species is the largest?
The largest crocodile species in the world is the Saltwater Crocodile (Crocodylus porosus), which is also the largest of all living reptiles. The saltwater crocodile is also the crocodile species that poses the greatest danger to humans.

The saltwater crocodile lives in eastern India, Southeast Asia and northern Australia. An adult male crocodile is typically 2.5 to 3 m long and weighs around 450 kg - but they can grow up to 7 m long and weigh more than 1,000 kg.