Generally, you don’t see conservatives arguing that conservative dominance of the political system would be good for liberals. But I’ve seen some - not many, but some - liberals argue that total liberal dominance would be good, not only for liberals, but also for conservatives. They argue that conservatives would get universal healthcare, a stronger social net, etc.
So - suppose for a moment that the number of conservatives in America remained the same, but liberals somehow owned all 100 Senate seats, all 435 House seats, the presidency, got all 9 justices on the Supreme Court, every federal judge was liberal, every state legislature and governorship was liberal, etc. (to avoid fighting the hypothetical, we won’t dissect how such an impossible situation could arise, let’s just assume it was that way.)
What’s the worst thing conservatives would face under such a scenario?
Abortion doesn’t affect pro-lifers, in the sense that it’s unlikely a pro-lifer would ever be forced to abort against their will, but it is perfectly possible that a pro-choicer could be denied an abortion if pro-life legislation passed.
Same-sex marriage doesn’t affect traditional-marriage supporters - nobody will ban heterosexual marriages, but gays may very well see gay marriage banned if it were the other way around.
Income taxes and many other taxes might increase steeply, but it’s not like conservatives are rich and liberals are poor. Plenty of conservatives are poor and plenty of liberals are rich. So such tax hikes would hardly affect one side more than the other.
Guns may be taken away, but there are Westernized democracies that fare pretty well with little to no gun ownership allowed (i.e., Japan and South Korea.)