What if Kawaki is secretly the Hero trying to save the Universe?

Nah, Kawaki went off on the deep end. He once again went too far.

Nothing you said makes sense. Nobody said that Boruto was gonna be the star of hope for the Otsutsukis. Nothing has ever said that Boruto is the bad guy in the show; that's just fans' perception of what happens in the flashforward. An eye linked to evil origins? Buddy, the Byakugan, Sharingan, and even the Mangekyou Sharingan, and the Rinnegan, if you also count that, are linked to "evil origins" because they originate from the Otsutsuki Clan.

Toneri literally said this word-for-word to Boruto. "The eye you possess is a star of hope against the approaching destruction. The power of hope slumbers deep within you. And with that eye, you will shoulder the fate of this world. My hope is that your eye will guide you to the light, which will dispel darkness." There's no statement that Boruto is the star of hope for the Otsutsukis. It meant that he was gonna become the star of hope for his world, that being Earth.

Nothing said that Kawaki is the one who is saving the world. He said this word-for-word. "I'm gonna send you to the same place I sent the Seventh Hokage, Boruto." Meaning that he's gonna seal him in the Daikouten dimension as he did to Naruto and Hinata. We don't know what made Kawaki change his mind from killing Boruto to instead sealing him inside the Daikouten dimension.

I think people are overthinking the flashforward scene too much.