How to beat the Doom hunter in Doom Eternal
Your very first priority in the Doom Hunter fight should be getting rid of his shield. The Doom Hunter is protected by a blue shield which will mitigate any incoming damage, but your Plasma Rifle can easily melt shields. Peel the boss with Plasma rifle until his shield shatters, then you move on to the next part of the fight, which is to kill the thing. Give the Doom Hunter all you've got. If you have Lock Shard mod for the Rocket launcher, use it here. Firing three rockets directly at the boss without having to aim makes this fight incredibly easy, and it should only take a few bursts to knock him down. If you prefer other weapons, just shoot the boss continuously while still moving in the arena. Keep these basic tips in mind and you should be successful. If you find yourself running out of health or armor, dismiss the boss for a moment and perform a glory kill on some of the weak demons roaming the arena.
After killing the Doom Hunter, you are ready for the second phase of the fight. This time there is two doom hunters separated to help you at the same time, which can be very difficult. Just follow the same strategy you used for the first Doom Hunter. Again, melt their shields with the Plasma rifle then use the Lock Shard for your Rocket launcher if you have it. Otherwise the Plasma rifle et Heavy cannon are great for dealing high damage while keeping your distance. Be sure and use your chain saw regularly, as you might run out of ammo at this point in the fight if you haven't already. If you are really having a hard time fighting the two Doom Hunters, try to fight them one by one. The arena is large enough to separate them from each other. Use this to your advantage.
It's a tough fight, but if you keep going you are sure to win in the end.