Killer Croc is the first boss that you face in Batman: Arkham Origins. He is one of the eight assassins hired by Black Mask to kill Batman, and a rather easy boss to defeat despite what his appearances suggest.
You will bump into him while tracking down Commissioner Loeb early on in Blackgate Prison. After Black Mask escapes by helicopter, Killer Croc will stay behind on the roof to take you down and bag that massive $50 million reward.
How to beat Killer Croc in Batman: Arkham Origins
The first thing to know is that you cannot hurt Killer Croc with your normal attacks. You cannot also counter his attacks, so do not make the mistake of treating him like any other normal enemy. You need to set him up for a beatdown.
The only way to defeat Killer Croc in Batman: Arkham Origins is to first stun him with your cape and then land a barrage of attacks before retreating.
You will have two opportunities to stun him. Every time Killer Croc charges at you, jump over him and then use your cape. If you are feeling confident, evade when he performs an attack. Whenever Killer Croc fails to land an attack, he will be caught in his animation for a few seconds. Quickly run up to him and use your cape to stun him.
During the boss fight, Killer Croc will grab one of the propane tanks to throw at you. This will be when enemies start appearing on the rooftop to join the fight. Ignore them and make sure that you hit the propane tank with a Batarang to make it explode. This will do a lot of damage to him.
If you fail to hit the propane tank, try to evade the explosion damage. This is important when fighting Killer Croc on hard difficulty in Batman: Arkham Origins. That propane tank takes away half of your life. You will not survive another blow.
Something else that you need to know about this boss fight is when Killer Croc grabs you. He will try to do that often, and you can use evade to escape. If he does grab you, he will try to bite you for a ton of damage in Batman: Arkham Origins. The only way to counter this is by smashing the button prompt on your screen.
As for the henchmen on the roof, they can prove to be annoying if you are playing Batman: Arkham Origins on the highest difficulty. You cannot keep ignoring them because they will try to stop you from reaching Killer Croc.
The trick here is to always keep Killer Croc in the center of your screen while evading and countering the other enemies. When Killer Croc comes near, use your cape to stun him for a beatdown.
Once defeated, you Killer Croc will be ready to answer your questions about Black Mask and the other assassins.
Killer Croc invisible bug
Batman: Arkham Origins is an old game, so there are likely a few bugs and glitches that still have not been fixed. If Killer Croc becomes invisible during the boss fight, you can follow the green marker on top of him. The propane tanks have green markers as well, so you will always have a general idea of his location.