I have a few contenders I've met , but three stand out to me;

1. The "guest" of an unfortunate flatmate I had some years ago. Scumbag came to stay with us for a few days after he had ingratiated himself with the flatmate (who didnt have the best judgement). I was already leery because he had facial tatoos, always a massive red flag. Within a week he had stolen some personal mail off me, a few CD's (this was when they still had real value) and a few other items. He ws driving and trying to sell a car at the time that I suspect was actually stolen. He stole a bunch of stuff of personal value from flatmate, and I started asking around town, turned out he'd stolen personal items from a bunch of people. We got a posse together to hunt down the piece of shit, but he disappeared.

• Year or two later his face turns up on TV, he was wanted for the kidnapping, sexual assault and anal rape of a four year old boy, along with using and dealing meth to kids. Oh, also it turns out he's a neo-nazi, something I had my suspicions of at the time but this was pre internet so I had no way to search his tatoos to confirm.

• So, neo nazi paedophile, meth pusher and all round scum. I did not like him very much.

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2. The partner of a good female friend of mine at a time she was very much at a low point and not making good choices. Also a neo nazi, gang member (Mongrel Mob a particularly evil vicious gang we have here). Fortunately she saw sense and split with him in fairly short order, shortly afterwards he was involved in a murder of some random stranger long with another gang member. Turned out he also had prior rape convictions as well, something which came as no surprise as that's a prerequisite for membership of that particular gang Apparently he chain smoked so heavily that he would wake up periodically through the night to smoke. Hopefully he's dead now

• I disliked him the moment I met him

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3. The ex-partner and long term stalker of a lady I had boarding with me. Only one of the three not to have facial tatts, but turned out to be just as much of a piece of shit. I caught him on my property multiple times, chased him off, disabled his car when I found it in our street, and also trashed his job as a taxi driver - that was funny as hell, the idiot had given me as a reference some months prior before he split with the lady boarding with me. They'd split partly because he'd tried to molest her young daughter (about 12 or so at the time) plus he'd been hanging round schools trying to pick up kids. The taxi authority guy in charge of vetting applicants called in to see me to dicuss his pending registration as a taxi driver, so I told him EVERYTHING. Next week the piece of shit didnt have a job.

• Shortly after that I caught him actually in the house, but the Police still didnt do a damn thing - as it happened he was also stalking someone else and got caught trying to burn their house down, he got put inside and while there got lippy with another inmate (absolutely typical for him) and he got the shit beaten out of him, was in a coma for months afterwards, and permanently disabled I believe. And that was the last I heard from him