I was thinking the about the Lesker dilemma the other days and came up with someone else who would love to bring him down: Nadja Daviar. I mean her and the Draco Foundation in Denver have been butting heads with Humanis for some time making which could be a good reason to bring Lesker down. But the real thing that could make Daviar want to take down Lesker is if he had some connection to Ares and Damien Knight, which I could easily see Lesker having due to Knight's recent move of Universal Omnitech to the UCAS section of Denver.
The problem, though, is Daviar wouldn't go for the strategic upfront kill as Colloton would. I'd see Daviar digging up as much dirt on Lesker as possible and releasing it to the public to ruin his image. Maybe even go so far as to bankrupt him and force him to live on the streets or such before finally at his lowest stage having him geeked. That could easily make for an interesting couple of jobs for some runners.
The other thing that came to mind while I was thinking is that if Colloton didn't want to appear as the one ordering the hit on Lesker, she could always tab Kay Street to help her. I mean it seems to me that Kay supports Colloton in her endeavors and Colloton could easily dangle the carrot of political power in front of Kay to get him to jump. Plus he'd have an easier time delving into the shadow community while keeping things quiet unlike Colloton.