There's a simple way to kill the RC once and for all: Reject the Mere Addition Principle. That's what I did, and what I think most people do intuitively.

To elaborate, there is an argument, that is basically sound, that if you accept the following two principles, you must accept the RC:

Mere Addtion: Adding a new life of positive welfare without impacting the welfare of other people always makes the world better.
Nonantiegalitarianism: Redistributing welfare so that those with the least amount of welfare get more than they had before is a good thing, providing their gains outweigh the losses of those it was redistributed from.

These two principles get you to the RC by enabling the Mere Addition Paradox. You add some people with very low welfare to a high welfare world. You redistribute welfare to the low welfare people. They get 1.01 units of welfare for every 1 unit taken from the high welfare people. Repeat until you get the RC.

So we need to reject one of these principles to avoid the RC. Which one? Nonantiegalitarianism seems unplesant to reject. Pretty much everyone believe in charity to some extent, that it's good to give up some of your welfare if it helps someone else who needs it more. So we should probably reject Mere Addition. We need to acknowledge that sometimes adding people to the world makes it worse.

Does rejecting Mere Addition generate any counterintuitive results? I would argue that at first it seems to, but actually it doesn't.

A philosopher named Arrenhius argued that rejecting Mere Addition leads to the Sadistic Conclusion. Basically, he argues that if adding lives of positive welfare can be bad, then it might be better to add a life of negative welfare than a huge amount of lives with positive welfare.

This seems bad, at first, but then I got to thinking. Arrhenius' Sadistic Conclusion was actually a special case of a larger, more general principle, namely that if it is bad to add lives of positive welfare, it might be better to do some other bad thing to prevent lives from being added. Adding a life of negative welfare is an especially nasty example, but there are other examples, people could harm themselves to avoid having children, or spend money on ways to prevent having children instead of on fun stuff.

Do people in fact do that? Do they harm themselves to avoid having children? All the time! People buy condoms instead of candy, and have surgeries performed to sterilize themselves! And they don't do this for purely selfish reasons, most people seem to think that they have a moral duty to not have children unless they can provide them with a certain level of care.

The reason the Sadistic Conclusion seems counterintuitive at first is that Arrhenius used an especially nasty, vivid example. It's the equivalent of someone using the Transplant case to argue against the conclusions of the trolley problem. Let's put it another way: Imagine that you could somehow compensate all the billions of people on Earth for the pain and suffering they undergo, and the opportunities for happiness they forgo, to make sure they don't have children. All you'd have to do is create on person with a total lifetime welfare of -0.01. That doesn't seem any less reasonable to me than tolerating a certain amount of car crashes so everyone benefits from transportation.

So we should accept the Sadistic Conclusion and reject Mere Addition.

What should we replace it with Mere Addition with? I think some general principle that a small population consisting of people with high welfare per capita is better than one with a large population with a low level of welfare per capita, even if the total amount of welfare in the larger population is greater. That's not very specific, I know, but it's on the right track. And it rejects both the Repugnant Conclusion, and the Kill and Replace Conclusion.