You own pre-concieved notions of yiddishkeit
Some of the posters mentioned people who will drive to shul on Shabbos, Eat without a Bracha, Wont wear Tfellin, Tzzizith, Might keep partial Kosher etc
You cannot give fire and brimstone to such people , you might act with love not hate. Give them a reason not to drive on Shabbos instead of telling them they are going to Gehenom if they continue to do it.
Which Mitzot to pick and choose for them to follow. Bringing up Tzinut or Mikvah for example might backfire