halacha - SE Challenge: Halachot in which rulings range from permissible to Torah violation?

Inspired by my previous question regarding heating up soup on Shabbat, I present a challenge to the Judaism StackExchange community --

List halachot which have halachic decisions ranging from outright Torah violations (i.e. not simply a rabbinic violation) all the way to 100% sanctioned and permissible?

For instance, regarding the soup question, Yemenite Jews follow the Rambam's decision that heating up liquids on Shabbat is fully permissible. On the other hand, the Shulchan Aruch (318:4) rules that it is a violation of the Torah.

(I am of course not referring to halachic decisions where decisors suggest that the righteous should refrain from such a practice, והבעל נפש יחמיר, etc. rather halachic decisions meant for communal consumption. Decisors often say, והעיקר הוא, 'the principle [decision] is' to denote their final, most basic decision).

Formal definition:

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  At least one halachic decisor must rule that the practice is completely permissible and this practice must be followed by at least one identifiable community (i.e. Sephardic Jews, Galician Jews, etc.)

  
  


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  Similarly, at least one halachic decisor must rule that the same practice is a flagrant violation of the Torah, with similar caveats as above.