Games like FUN.IO : Arena Battle
Games like FUN.IO : Arena Battle include Vampire Survivors, Deep Rock Galactic: Survivor, BALL x PIT, Nova Drift, and Megabonk. We matched them by the tags players give FUN.IO : Arena Battle on Steam (Action, Casual, Beat 'em up, Arena Shooter, and Bullet Hell): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Bullet Hell · Action Roguelike · Casual

Deep Rock Galactic: Survivor
Shared: Bullet Hell · Action Roguelike · Arena Shooter

BALL x PIT
Shared: Action · Bullet Hell · Arcade

Nova Drift
Shared: Bullet Hell · Arena Shooter · Arcade

Megabonk
Shared: Action Roguelike · Action · Bullet Hell

Streets of Rage 4
Shared: Action · Beat 'em up · Arcade

Planes, Bullets and Vodka
Shared: Action · Casual · Bullet Hell

One Finger Death Punch 2
Shared: Action · Beat 'em up · Casual

Brotato
Shared: Bullet Hell · Action Roguelike · Arena Shooter

One Finger Death Punch
Shared: Action · Beat 'em up · Casual

Halls of Torment
Shared: Bullet Hell · Action · Action Roguelike

Windowkill
Shared: Action · Bullet Hell · Action Roguelike

Boneraiser Minions
Shared: Bullet Hell · Action Roguelike · Casual

Glyphica: Typing Survival
Shared: Arena Shooter · Action · Bullet Hell

Death Must Die
Shared: Bullet Hell · Action · Action Roguelike

Commando Collection
Shared: Action · Beat 'em up · Bullet Hell

Cyberhunt
Shared: Action · Casual · Arcade

Rocket Rats
Shared: Casual · Bullet Hell · Action

Enter the Gungeon
Shared: Bullet Hell · Action Roguelike · Action

Timberman
Shared: Casual · Action · Arcade

Bit Blaster XL
Shared: Bullet Hell · Action · Casual

Downwell
Shared: Action · Action Roguelike · Arcade

FatalZone
Shared: Bullet Hell · Action · Action Roguelike

Noobs Want to Live
Shared: Action · Bullet Hell · Casual