1. Increase the Level of Your Enemies: As you progress through the game, you'll unlock new levels with increasingly tougher enemies. Higher level enemies will have more health, deal more damage, and might have unique abilities that make them more challenging to defeat.
2. Choose Higher Difficulty Levels: While not a true "hard mode," some stages in the game have different difficulty settings. Choose the higher difficulty level to face tougher enemies and a greater challenge.
3. Focus on Difficult Missions: Certain missions in the game offer special challenges or increased rewards. These missions often require strategic thinking and more challenging gameplay, making them great for testing your skills.
4. Limit Your Resources: If you're looking for a truly hardcore experience, try playing with limited resources. This could mean limiting the amount of health packs you use, restricting yourself to using only certain heroes, or even trying to complete missions without using any special abilities.
5. Participate in Special Events: Justice League: Final Defense often has special events with unique rules or challenges. These events can offer a chance to play in a new way and push your skills to the limit.
6. Engage in PvP Battles: While not directly affecting the difficulty of the main campaign, engaging in player vs. player (PvP) battles allows you to test your strategies and team composition against other players.
Remember, it's important to find a balance between challenging yourself and enjoying the game. Don't be afraid to experiment and see what works best for you!