Paul Kent was an obvious one, but hopefully his influence is now squashed.
Gould I reckon, would be up there. Great if he's at your club and engaged, but Trump-esque in his lies, his chest-beating, his death riding parts of the game, his promotion of 'fake news' around rules of the game etc.
Player agents can be scum, some are fine I'm sure but the ones that encourage players to lie down or get out of contracts they should commit to, are the vermin that causes issues in the game.
I dunno if there are many others? Ricky Stuart is a germ but honestly, Canberra love him and he's largely irrelevant because they are nowadays, so no real issues there. Then there's the other cretinous media types like Hooper, Rothfield and co.