★ krow! ★

As a beginner ninja, both Morro and Kai dealt with arrogance, recklessness, and anger. We see this in how Morro took extremely dangerous risks to get Wu to save him, with how he assumed he was to be the green ninja when Wu told him he believed Morro was to wear green, and how Morro reacted when the weapons didn't react to him (ripping off the sliding door). We see this in how younger Kai jumps into situations without a genuine plan, how he gets angry and often (literally) explodes with fire when something frustrates him, and how he kind of defaults to the coolest person on the team/the hot one/the center of attention/etc when that's just really the immature persona he's thrown up to try and be the best.

Both Morro and Kai want to be the best at what they can do, and when they heard about a chance to be even better than their original concepts of the best (becoming the Green Ninja), both of them jumped at it.

Morro trained so hard he ended up hurting the kids he was training against and worrying Wu

Kai tried so hard to be the green ninja he ended up placing unnecessary strain on his relationships and even went so far as to risk letting people get hurt/die because he was prioritizing what he thought might get him closer to being the Green Ninja (a competitive line of thinking that Kai's been known to buy into in addition to his constant needs to try to be the best in the situation before he matures) (btw I'm talking about him originally trying to get the fang blade instead of. yknow. the CHILD about to burn lol.)

So, where do we see the shift from heroic to villanous in these two suspiciously similar characters? Well, it's when both of them are placed in an inferno scenario where they have to choose between pursuing their perceived destiny and their true destiny; hence, the inferno of destiny parallel.

Morro

When Morro searches so long to try and find a way to become the Legendary Green Ninja and rewrite destiny, he eventually finds himself in the Caves of Despair. We don't have the details of what happened, but we see the ninja try to escape Morro's fate in season 5 episode 7 titled "The Crooked Path". Here we see them encounter geysers that are releasing poisonous gases at an alarming rate, and they also spray boiling water/steam out in addition to rising the temperature to an unbearable level in the cave. It's reasonable to assume that Morro experienced a cave-in due to the caves' lack of structural integrity (also experienced by the ninja)* and then was killed either from burns from the hot steam and/or due to inhaling too much of the dangerous gasses.

The point of Morro's inferno: Morro couldn't accept the fact that he was not destined to be the Green Ninja, so he wasn't willing to turn away from his perceived destiny to save his own life. He wouldn't leave the cave because he couldn't let go of the fact that his perceived destiny wasn't his true destiny.

Kai

When Kai trains and practices to become the Green Ninja, making rash decisions (like jumping down for the Fang Blade again) and reckless choices that hurt his relationships (like barricading himself into a room to fight Garmadon for… literally no reason other than his desire to be the Green Ninja), he eventually finds himself in a similar inferno: The Fire Temple. An ancient temple constructed inside a volcano that once held the Sword of Fire, this is where the fourth and final Fang Blade is located and where the ninja must fight against Pythor and the other Serpentine generals for it. The volcano begins to erupt and collapse in on itself, and Kai ends up with a choice: save young Lloyd from his inevitable death in the erupting volcano, or try to reach the Fang Blade before it ends up in the hands of Pythor. This is the critical moment* for Kai, as he has to choose between his percieved destiny (becoming the Green Ninja and getting the Fang Blade) or his true destiny (protecting Lloyd in the hopes of saving both of their lives). In the end, he chooses to give up the thing he'd been working towards for most likely months now to try and be the best in the favor of saving a kid that used to be a massive pain in the ass (no offense, little Lloyd).

The point of Kai's inferno: Kai gave up his perceived destiny in the end, and only then was he able to unlock his True Potential in addition to being able to escape the Fire Temple safely with Lloyd and himself still alive. He was able to save himself and Lloyd because he gave up something that had felt like such a core part of his being, that he believed was his destiny, even though it turned out not to be.

He even says this himself to Sensei Wu: "I knew when I had to make a choice. I wanted the Fangblade so badly, to prove I was good enough to become the Green Ninja. But then I figured it out. All of my training to become the best ninja wasn't in preparation to become the Green Ninja. It was… to protect him." (s1e10, titled "The Green Ninja")

Kai and Morro both experience infernos that threaten their lives and rely on their ability to relinquish their percieved goals in favor of the objectively best choice in the moment. Morro was unable to give up what he truly believed was his destiny, and he ended up dead and sent to the Cursed Realm as a result. Kai was able to give up what he had been working towards for so long, and was able to save his life and Lloyd's life (especially entertaining when you remember that Kai had to give up trying to be the Green Ninja to… save the Green Ninja, lmao)

The critical moment I noted with a * for both Kai and Morro is that this point is the moment where each of them have to decide what's more important to them: what they believe is their destiny, or what would save their life. Morro tried to push through to his "destiny" and became too hurt or sick from the fumes to escape, and eventually died there. Kai gave up his "destiny" and just barely managed to escape with his life and Lloyd's.