When you're behind, the enemy has more gold, more items, and more stats. In a fair fight, you lose. Your job is to never take a fair fight.
Comeback strategies:
• Defend under towers. Towers are the great equalizer. A 5k gold lead doesn't matter if the enemy has to dive you under a tier-3 tower.
• Look for picks. The enemy will get overconfident. Someone will face-check a bush alone. Punish them.
• Stall for late game. If your comp outscales (Luban No.7, Liu Bei), your only job is to not lose before 15 minutes.
• Trade objectives. They take Overlord? You take their tier-2 tower on the opposite side. Don't contest — trade.
The biggest mistake when behind: forcing a fight because you're frustrated. Frustration loses more games than skill gaps.