I've been feeling like I've been getting bullied lately, what with all the demons and blood-suckers and whatever, and I don't know what to say back......

In your case, there's no need to play word games.

If you're going to do it, simply say "Die" and do it.

It's all about momentum!

You should be able to scare them with just a knife! ドス 'dosu', a dagger.

......! "Don't die"!? 死ね 'shine' - "Die" from before, plus どす 'dosu' - "knife" from before = 死ねどす 'shinedosu' - "Don't die"