While I can see why your character would struggle with this, morally, my view is that his struggle is because he's an emotional 12-year-old with a heart of gold and a lack of experience. He struggles with it much as a 12-year-old might struggle with playing high school football or performing high school calculus.

That is to say, this isn't a moral dilemma; it simply is not a problem to which he's yet mature enough to know and understand the solution. Not intellectually. Perhaps unfortunately, his instincts lean towards the "every life, no matter how evil, is precious" more than towards they "good guys vs. bad guys" paradigm. Both are immature paradigms which refine into a single non-contradictory whole when fully and maturely examined, but currently - to Ricardo - the former contradicts the latter.

The correct answer - which I can say much as I could easily tell a 12-year-old what the derivative of f(x) = x*x is - is to kill her and possibly stick around long enough to make sure the people taking power are more "good-aligned." I can also go into detail and explain why, again much as I could explain the limit theorem of calculus and how it relates to derivatives. But that doesn't mean it'd be easy for Ricardo to accept.

So, that brings us back to the point that it's easy to see why this is a dilemma for Ricardo, but would not be one for a mature and philosophical character who shares Ricardo's apparent ideals. Or at least the ideals he's growing to develop.