(1) To solve ( D ) you have to destroy the narcissist because nothing else will work. Figure out whats a sore point for them by watching who they target (looks, intelligence, weight, popularity, confidence, etc). Lets take looks as the example. Whenever they are next to someone more attractive be it a manager or work colleague openly point it out. They will quickly self destruct and turn others against them.
(2) To solve ( E ) treat other people nicely and never let people hear you being negative about others. In addition bringing in a tin of roses every once in a while and letting everyone have one makes you liked. As a result they wont believe any bad mouthing about you.
(1) What an appalling bully this reveals you to be! You never, ever destroy anyone. I have described ways of dealing with bullying, but none of them resort to bullying. In fact, they ALL turn things around and offer positive ways forward for everyone, they allow everyone to walk away with their pride and self-respect intact. I repeat, THIS TACTIC IS STAGGERINGLY BRUTAL, and anyone on this forum who was nodding as they read this, can know, if they did not before, that they are a bully.
(2) Have you no self-respect? To BUY favour!!!!! Offering roses to all and sundry to get them to like you??? That is just SO low. And the thing is, that that kind of crawling does not buy you what you are looking for. People will laugh at you behind your back and take a loan of you. The last thing they will do is actually respect you.