The thing about Liu Kang is, I honestly find him to be a really interesting character as originally conceived, but I feel like the idea of Liu has been lost over time.
Liu Kang as originally conceived is something of a more heroic Son Goku archetype. Liu Kang is a master martial artist who's dedicated himself to his craft with every day of his life. He grew up in a monastery training to one day represent his realm in the Mortal Kombat tournament, and the knowledge that this would be his path has defined every moment of his existence.
As Champion of Mortal Kombat, he is the most skilled fighter in the realms. Through skill, discipline, and decades of training, he's become so talented that he can outfight gods, demons, sorcerers, and whatever else the multiverse can throw at him.
But he's also a pacifist. As a Shaolin monk, Liu Kang holds a deep reverence for life in his heart. In a franchise notable for its brutal violence, Liu Kang is notable for his sense of mercy.
-> He defeated Goro in the Mortal Kombat tournament, then spared his life.
-> He defeated Shang Tsung in the Mortal Kombat tournament, then spared his life.
-> He defeated Kintaro in the Outworld Tournament, then spared his life.
-> He defeated Shao Kahn in the Outworld Tournament, then spared his life.
-> He defeated Shao Kahn again in the invasion of Earthrealm, then spared his life.
-> He defeated Shinnok, then... Well, Shinnok's a god and was returned to the Netherrealm so it's a little different. But still.
He didn't even have a real Fatality in the first game, but rather a bloodless finisher. Liu Kang was the first character ever to have a Heroic Brutality.
Liu Kang is the strongest fighter of them all, and he reveres life absolutely with religious fervor.
As Mortal Kombat's central hero, this is what makes him distinct. And it is that contradiction, that juxtaposition of a man like this as Mortal Kombat's central hero that makes Liu Kang an interesting character. It's the fact that a man like this can walk through this dark and cynical world of murderers and soul-rippers without being consumed by it, holding true to his values and defending life in all its forms.
Liu Kang is such an interesting hero, y'all. He's Avatar Aang in Game of Thrones.
But it feels like modern Mortal Kombat has kinda ruined him. Like. It feels like modern MK has missed the point in their attempts to revise him to make him "more interesting".
-> He should kill people. This is Mortal Kombat. Everyone kills everyone here. Why would there ever be a character who doesn't kill people?
-> And he should only be a good fighter, not the best fighter. Definitely not on the level of people like Shao Kahn or Shinnok. Just a mid-tier good fighter guy.
-> Also, a mid-tier good fighter guy who kills people is a boring protagonist. He shouldn't be the protagonist. He should just support the real protagonists and stuff.
-> Or we'll make him a god! If he's a god, then we can justify him nuking all the villains with his infinite god powers!
Of course he's a boring protagonist if you strip out the elements that make him interesting. If he's not a pacifist and he can't outpunch gods and he's not the hero and he ultimately loses, yeah, what little remains of him makes for a pretty boring side character.
But that's not a problem of Liu Kang being uninteresting.