At least for Germany the legal basis was already laid last year when the "progressive" government of social democrats (SPD), Greens and (neo-)liberals (FDP) passed a revamped citizenship law. They allow for dual citizenship but also passed that you can loose your citizenship if you don't become stateless.
Then multiple states made a requirement that you need to sign a paper in your application process, where you say that you agree in "Israels right to exist". The caveat is that this term is nonsensical in a legal sense (there simply is no codification of a "right of existence" for states) and deliberately ambiguous in a political sense. (In which territory, with which government, with which people? Is calling the current government fascist an attack on the state itself already?)
So whenever a citizen speaks up against actions of the state of Israel, goes to a demonstration, likes the wrong social media post... German authorities could revoke the citizenship based on saying he lied on his application. This does not require a criminal conviction and is much more difficult to challenge as "lying" on your application is a sufficient formal reason. IIRC the law isn't even limited to dual citizens but it is enough if the person would not become stateless if Germany revokes their citizenship. This is for instance the case for people who are claimed as citizens by Iran, as Iran does not recognize people renouncing their citizenship.
https://en.wikipedia.org/wiki/Ammonium_nitrate_disasters
I think the largest in scale and death toll were Oppau and Texas City