Killmonger coming back cheapens the finale of the first, for obvious reasons. Ive said this elsewhere: everything that happens in Wakanda as a result of opening its doors to the rest of the world will be directly tied to Erik. You dont even need a vision in the afterlife, just a reminder of the lasting impact of the clash of ideology. TChalla had the outreach center built where Killmonger grew up in for a reason - to make to make right what his father had wronged. See? Much more potent.