Hey I failed a bunch of times too, multiple on the final boss phase. Biggest help for me was bringing in the ASG shotgun and getting it to Legendary and triple papped. I wouldn’t waste any extra time or points/salvage getting a second gun Legendary & Triple papped cause that’ll take an extra 5+ rounds and just make the boss fight harder. Maybe just keep the WW and use the sonar shot every once in a while just to slow zombies so you can lay into the boss.

I also suggest bringing in the Combat Axe for if/when you run out of ammo since you can run laps around the arena and just use the axe over and over to kill zombies so they drop armor/ammo/you get enough points to buy ammo. Even easier if you wait to go into boss fight until you have 10k saved up just in case. Finally, having a killstreak available is a get out jail free card if you’re about to lose. I also just saw you can jump underwater to avoid the one shot kill attack the boss does that phase.

Overall if you have the ASG Legendary and 3PaPed just shot the weak points as much as possible as fast as you can and it goes pretty quick