One who is fond of fighting

The correct answer is bellicose.

• Bellicose means eager or likely to fight; warlike.
• Aggressive means ready or likely to attack or confront; forceful.
• Belligerent means actively involved in or carrying on war.
• Militant means actively involved in or promoting a particular cause, especially a political or social one.

In this case, the correct answer is bellicose because it is the only option that specifically refers to someone who is fond of fighting. The other options, while they may be related to fighting, do not specifically refer to someone who is fond of it.