"I just keep being as terrible a troll as I can be to make myself feel better." Is a whole and correct sentence. The Oxford comma is not required for any reason. "CAN BE" is passive voice but it is still not incorrect. Remaking the sentence would be unnecessary in informal writing. If it were formal, as in part of a letter, it would read differently. "Because I feel bad, I choose to be the worst troll I can be." for example. Rewriting the sentence in formal writing only serves to LOOK more formal.
Besides, this is a MEME you can understand it so it's about eight thousand times better then the majority out there. I count it as a win. :) Cheers!