死就是死

"不得好死" is a very common curse.

But strictly speaking, 死就是死, 管他个好死还是坏死呢?

As long as one lives, there is hope, be it 生不如死 or not. Once dead, there's nothing, absolutely nothing, for that person anymore.

In that light, maybe "祝你早死" would be a better malediction as compared to "不得好死" and "生不如死", for (1) the other two means letting the person suffer, that's not very nice, and (2) there's a "祝" there oh, which is polite.

当然，以上只是建议，没有恶意，请不要(太)在意。