I don't understand whatever happened to using google to answer these questions?
Read this:
https://forgottenrealms.fandom.com/wiki/Eilistraeeor
Watch/listen to this:
https://www.youtube.com/watch?v=a9NxhuwbiRAEdit: Canonically, if a cleric/paladin of a good aligned god would flip a switch and start randomly killing innocents and committing other evil crimes, they would lose all the powers granted by their gods. Paladins would become oathbreakers essentially. Clerics would not be able to cast any spells until they atone and even then a lot of deities wouldn't forgive them as easily.
I know you used the link to FR wiki in your post but you seem to not have read the contents?