question

Peace and blessings
question:
A. I'm not so clear on how Shas is filled with stories about our rabbis who, if someone did something wrong or said something wrong, burned him with a glance [Rashbani, Rabbi Yochanan, and there are others] A. They didn't care about killing people? B. Is there a prohibition against killing a person with a glance?
on. It is explained in the Sanhedrin that this heretic despises the Holy Scriptures. Is he a heretic for the reason that he is killed or only for the reason that he does not have a next world?
Regards
A.I.A.