@BBY_YOD4
I did not say not to fight him at all, don't put words in my mouth, i told you to fight him at mid range where he can't use his gas on you. Seek the high ground when possible cause the gas isn't nearly as dense or high as you think, verticality is your friend, you often see him better than he does you if he hides in it. Use grenades to get him back into your LoS if he retreats.
Don't just rush him with your R99 or Prowler and think 600 bullets crammed in your inventory is going to help you. Thats like trying to counter landmines in games by checking them with your feet.