Borderlands 3

To start the Arms Race, you have to accept the mission via a poster on the wall opposite the Lost Loot Machine on Sanctuary III then Fast Travel to the Stormblind Complex (it's in the Pandora sub-menu of the Galactic Map) and complete a short mission for Axton and Salvador. Arms Race is the Borderlands equivalent of Battle Royale (only with no Royale and not much in the way of Battle) but you will start every run with nothing except some ammo and unmodded Grenades which means no Guardian Rank, no Action Skill, no Weapons, no Shield etc. etc. so you have to acquire everything on-site from either chests, lockers, rubbish/Skag piles or fallen enemies.
 
Here are some general tips:
 
Locate a loot source immediately! Without a gun and a shield, you are as good as dead but with luck there will be a chest near to where you land so seek it out and claim the content. Your initial gear will be pretty rubbish but it's better than nothing. If possible, try and acquire at least one elemental weapon and an Atlas Rocket Launcher so you stand a better chance against the final boss. Also note the Legendaries that are unique to this DLC, can't be used until after they have been extracted but all others can be used immediately.
 
Keep moving but look for cover if you come under heavy fire - A stationary target is a dead one so keep moving and don't stop, unless it's to pick up a new weapon or Shield or have come under heavy fire.
 
Know thy enemy - With the exception of the final boss, all the enemies in this DLC are reskins of ones found elsewhere in the game e.g. Skags, Spiderants, Bandits, Heavies etc. etc. so do your best to pick the right weapon for the job, from your limited arsenal. The most annoying enemies are the Revenants, Badasses and anyone carrying a Riot shield.
 
The Murdercane is no joke - The Murdercane is exactly like it sounds, i.e. a Hurricane of death, only this one is made up of ice and shards of metal so will tear you apart very quickly if you get caught in it. Keep an eye on the timer beneath your mini-map, because that will tell you the current status of the Murdercane and how long you have left before it either starts moving or stops if it's already moving. The longer the round lasts, the smaller the playable area you will have to run around in.
 
Keep the Treat Yo Self and Complex Made Simple trophies in mind - Both of these trophies will take multiple runs to get so make sure you methodically explore the Stormblind Complex and locate any areas you're missing, along with keeping an eye out for the Gear Extractors (more about those in the Treat Yo Self  walkthrough) and extract any loot you're not using.
 
Airdrops aren't your friend - Periodically, Airdrops will appear and give you a chance at better gear but you will be greeted by a ton of enemies and run the high risk of getting your butt handed to you so don't bother unless you're desperate for better gear.
 
Don't die! If you die, you will lose absolutely everything that wasn't extracted and have to redo the entire round from scratch.
 
Save your money - Whilst you will earn a reasonable amount of cash during a round, it's best to save it for use with the vending machines outside the boss arena so you can refill your ammo and health or buy a better Shield and/or Grenade.
 
Borderlands Science Boosts are your friend - The temp Boosts you get from the Borderlands Science machine in Tannis's Infirmary on-board Sanctuary III will make life much easier so it's spending a few mins grinding out 500 - 1,000 Credits to buy one that catches your eye. Each Boost lasts for 1 in-game hour so make use of them but do note you can only have 1 Boost active at any given time so choose wisely.
Boss details:
 
Heavyweight Harker: Fought during the mission "Arms Race" but you can enter his arena at any time, provided you have sufficient firepower to kill him.
Heavyweight Harker has the following attacks:
 
Elemental/Non-Elemental Assault Rifle/Shotgun - Depending on what the RNG decides to give him.
Elemental Grenades
Enemy Spawn
Energy Pulse
Hound Spawn
Melee
 
Note: If you get stuck, please use the Boosting Thread to find someone to help you: LINK
 
Phase 1: During this phase, you need to focus on getting rid of Harker's Shield so use any Shock weapons you have available. If no Shock weapons are available, then use whatever you have that is powerful with a decent rate-of-fire. Harker will use Elemental weapons against you but since the odds are you won't have anything to resist them, you will have to weather his attacks as best you can. The most dangerous attack you have to watch out for is the Energy Pulse so run to the other side of the room once you see the beam emerge from the mouth of Harker's hound. Once his shield is gone, use your best available weapon to get rid of Harker's hound (which also doubles as his armour). Make sure you don't get too close to him.
 
Phase 2: With his defenses and hound gone, Harker will fall to the floor then start following you around the room so use the limited amount of cover to protect yourself from his attacks whilst you whittle away his health but watch out for his Hound, because it can do some serious damage if it gets too close.. Once he's toast, the trophy will pop.