This is mainly pertaining to people that think they are invincible in the forest (Gyu, Sin, Takumi. And I STILL HIGHLY disagree Gyu should have Sannin privileges at a damn Jounin level).
Instead of the enemies growing with your DK count, have them go on defense and attack.
For example: I have about 91 defense at level 1. Have the enemy.. Let's say... have five less defense than my total, including temporary (armour/events). So they will have roughly 86 defense.
The same will be for attack.
This way, it'l; make them have a chance at dying.
I know it's hard work, but nobody should EVER be invincible.