Which is more forbidden and carries a graver punishment: tale-bearing and discord-mongering, or adultery?

Backbiting [namimah (definition)], adultery [zina], and sowing discord [fitnah] among people are among the greatest of major sins [kabair]. All of them are major sins, and no differentiation in their prohibition has been specified. Adultery is unique in that it carries a prescribed punishment [hadd] in this world. The gravity of any major sin is amplified depending on the situation, time, and place. A backbiter [nammam] is someone who conveys harmful speech between people to sow enmity between them. The Prophet, peace and blessings be upon him, said: "A backbiter will not enter Paradise." Backbiting is one of the causes for entering Hellfire, unless the transmission is for a beneficial purpose, such as warning against evil.