Demon of Justice is described as 'Take control of the weaponised satellite 'Demon of Justice' and use it to save cities around the world from being invaded by demons!'. There are three games similar to Demon of Justice for a variety of platforms, including Mac, Online / Web-based, Windows, Steam and Android. The best alternative is Enter the Gungeon. It's not free, so if you're looking for a free alternative, you could try Utilizer Deluxe or Slay.one.
Enter the Gungeon is a bullet hell dungeon crawler following a band of misfits seeking to shoot, loot, dodge roll and table-flip their way to personal absolution by reaching the legendary Gungeon’s ultimate treasure: the gun that can kill the past.
Utilizer Deluxe is a mobile arcade space shooter mixed with a match 3 genre! Utilize fancy space monsters, fight with dangerous bosses, make color blocks combinations, upgrade your spaceship, complete all sectors and test your skills in the survival mode!
"Slay.one" is a free multiplayer top-down shooter which you can play directly in your browser - no install required! Features the game modes Deathmatch, Team Deathmatch, Ranked, Zombie Deathmatch, & Capture the Flag!