In the Boss Fight Event, five players battle one player's "Boss" Brawler. The Boss has very high health, improved damage output, and enhanced abilities, but their ability to self-heal is removed. Instead, The Boss has a health decay that removes a couple hundred health every second. The Boss attempts to stay alive for as long as possible while the others try to defeat the Boss as quickly as possible. The time on the clock when the Boss is defeated determines how many Keys the participants receive. The Boss "wins" the mode by surviving past 2 minutes and 5 seconds, for which they receive the most Keys. Likewise, the normal players win by defeating the Boss in under 2 minutes and 5 seconds. Because of the health decay, the maximum survival time of The Boss if they were not to be damaged at all by the opposing team would be about 5 minutes. This is an unranked mode, so Trophies cannot be earned or lost.
- Mortis: The Boss's reload speed is greatly increased in this Event. Because of this, Mortis as the boss would be able to escape bad situations and kite the opposing team for a long time with his dash. He can also damage a few Brawlers in the process.
- Jessie and Nita: Both of these Brawlers are useful because their Supers spawn either a turret or a Bear. Both have greatly increased damage and health, and it can be useful for taking out opponents or distracting them for you to take as minimal damage as possible.
- Crow: Crow is very useful as his fast movement speed allows him to escape from bad situations and kite opposing team, he can also use his poison to prevent them from healing.
- Shelly: Shelly can get up close to the boss, if she gets close enough to the boss and charges up her super, she can consistently chain her super over again quickly, her damage in close range is high enough to overwhelm the boss as long as she‘s being supported.
- Barley: When he has his super charged, and the boss is being slowed down or stunned At the same time, Barley will have enough time to get close to the boss and burst out his super, the boss will take heavy damage if he/she can’t escape quickly. Even without his super, he can safely hide in bushes or walls to throw his bottles at the boss.
- Darryl: Similar to Shelly, Darryl deals very high damage in close range. If he does get taken out, when he respawn, he can use his super to roll back to the boss quickly, and continue to deal heavy damage.
- Frank: Frank charges up his super very quickly, and when he’s within range of the boss, he can use his super to stun the boss for 3 seconds, allowing other brawlers to deal good amount of damage before the boss can move again, he can also use his super to break walls, reducing the area in the map where the boss can hide
- Spike: Spike’s high damage allows him to be a consistent damage dealer, he can also use his super to slow the boss down, giving advantage for the team to attack the boss.
- Bosses can get more Keys the longer they stay alive. Instead of fighting, you can simply run away from enemies to last longer.
- Attack the Boss from all sides in order to overwhelm them.
- If the Boss is a single-target attacker, try to attack them all at once. If you just send Brawlers in one at a time, the Boss will be able to pick off the individual Brawlers more easily and survive longer.