Bubalus palaeokerabau
Bubalus palaeokerabau is an extinct species of water buffalo that was endemic to Java during the Late Pleistocene. B. palaeokerabau can be distinguished from more recent domestic water buffalo introduced to Java by their larger size and their extremely long horns, which can be around  long from tip to tip. References

Prehistoric bovids
Pleistocene even-toed ungulates
Pleistocene mammals of Asia
Pleistocene extinctions
Extinct animals of Indonesia