I don't believe random characters that can be killed are required for 100% completion, just the same as it's only Brucie, Jacob, and Packie that you have to do the friend stuff for.
Originally Posted by Drumbot8500
At this point, I'm pretty clueless as to what I must've forgotten. All's I know is it has to be something worth 1.25%
Strangely enough, there is nothing listed required for exactly 1.25% (via GTA4.net's 100% checklist).
Although my best guess at this point is to check the races. There should be nine total, 3 in Alderney, 3 Algonquin, and 3 on the Eastern boroughs.