Trevor kills some Lost brothers, Franklin kills some Ballas, Michael fends off some of Madrazo's guys,
But that's another problem I have, technically if you do all Side Missions, then TREVOR ends up killing MORE Ballas than Franklin. Two out of the three major mission that involve fighting with the Ballas Trevor is there, leaving only The Long Stretch to put Franklin ahead, but then Trevor takes on multiple waves of Ballas in Rampage Four which easily outclass the ones you fight in The Long Stretch.
I just really think ALL stories could have been handled better, but especially Franklin's, like I pointed out, mansion onwards he's just, well, there, the earlier cutscenes with Lamarr and his Aunt and Toya, etc, were much more interesting and felt like properly written stuff compared to the mansion version where he's just, well, not doing much except waiting for missions.
If the story was properly paced, instead of being so one sided with the FIB sh*t, then the last mission, Option C would have had Trevor fighting The Lost MC, Franklin go against the Ballas in a final takedown, and Michael still against the FIB. I mean sh*t, in Mr Phillips, not only does Trevor go against The Lost MC, but there's also one part where he trashes a meth lab owned by the Aztecas, ...and nothing becomes of it. Hell, if they did the gang stuff properly, that there would have been an action packed story, Trevor Vs. The Lost MC and Aztecas, Franklin Vs. Ballas, BUT also helping Trevor against the Aztecas, and then the FIB stuff with Michael as it already is.
edit: And just to point out, that sh*t would have worked, it would have gave Trevor a reason to fight the Ballas with Franklin outside of "oooh he's crazy and likes this" as it would have built up a relationship with Franklin as they'd help each other out with the gangs, sh*t, just think of a mission that could have worked where the Aztecas attack Trevor's airstrip or some sh*t and he calls in Franklin, Lamarr and some Families for help as payback for helping them in the Grove St fight.