* Excessive Strain: The Kaio-ken significantly amplifies Goku's power, but it comes at a heavy cost. It puts immense strain on his body, leading to severe fatigue, injuries, and even potential death if used for prolonged periods or at higher multipliers.
* Increased Risk: The Kaio-ken's risk outweighs its benefits, especially with Goku's current power levels. He's reached a point where he can achieve comparable power boosts through natural training and mastering new techniques.
* Alternative Techniques: Goku has developed a range of powerful techniques that provide him with safe and effective power boosts, such as Super Saiyan transformations, Ultra Instinct, and even mastering his own energy manipulation (such as using Ki blasts to enhance his speed and agility).
* Storytelling Purpose: The Kaio-ken was a crucial part of Goku's early character arc and served as a symbol of his determination and willingness to push his limits. However, as the story progressed, it became less relevant and more of a liability.
While Goku occasionally uses the Kaio-ken in Dragon Ball Super, it's generally for brief moments or in situations where he needs a temporary power boost. However, he no longer relies on it as his primary means of amplifying his strength.
Ultimately, the Kaio-ken is a powerful but dangerous technique that Goku has learned to leave behind in favor of safer and more sustainable methods of achieving his full potential.