I Am Legend 2 will follow the alternate ending of I Am Legend, which means the upcoming sequel has a significant villain problem. Each ending of the original movie identified a different villain, with the alternate ending following the idea of the book that Will Smith's character, Robert Neville, was the true bad guy of the story since he had been capturing, experimenting on, and killing the Darkseekers. This realization established the themes of Neville's story, but by retconning the ending and keeping Neville alive, I Am Legend 2 will have difficulty following this up cohesively.
https://screenrant.com/i-am-legend-2-villain-neville-problem/