Why throw T'Challa over the waterfall? and way to fix it
Killmonger could have easily finish T'Challa right there before everyone's eyes, it would be in line with his cruel nature ,could have slit his throat or broke his neck in front of everybody instead he threw him away as if to save him WTF?
Easy way to fix it:
As Killmonger is about to deal the fatal blow, Zun thew himself on T'Challa and block with his body as repayment to his father. With his dying breath he urge T'Challa to escape but T'Challa refused ,then with the last of his strenght he push T'Challa off the edge of the waterfall(the end of the fight would have to be much closer to the edge for this scene).
Killmonger was declared winner after they cannot find T'Challa and was presumed dead.In the movie they didnt even tried to look for him or his body which is weird.