Those probably just weren't all specific enough. A titan can only be killed by cutting out the nape of its neck. A Balteus vampire can only can only be killed if you go through a whole process. Anything can be killed.

[Hajime at some point you're gonna get yourself killed and Eren's just going to say "I told you so."]

I'm nobody's toy! And we can't count on that, not with everyone's lives on the line! So how would we decontaminate here? More technology crap?