Hardly anyone will have heard of these people but no matter - they're as repellent (IMO, anyway) as anyone named here, if not more so.
Shane Warne. As a cricketer, he is / was exceptional. As a human being, he's a disgrace - an arrogant, spoiled, attention whoring arsehole who seems to think everything should revolve around him and who refuses to accept any responsibility for or consequences of his actions. Lleyton Hewitt is a saint compared to Warne.
A couple of people have mentioned Jana Pittman / Rawlinson. She's at least achieved something on the world stage, but she's so damned full of herself and is such a whiny drama queen it's very difficult to admire her for it.
Tamsyn Lewis, who's achieved
nothing on the world stage yet expects to be praised and fawned over as though she's the female Michael Johnson.
Anthony Mundine, who has an ego the size of the cosmos, is racist (and plays the race card at every available opportunity), bigoted, sexist, arrogant beyond belief, and has built a record in boxing by fighting people no one's ever heard of. Seeing him flattened by about the only "name" boxer he took on is by far the best thing I've seen happen in a boxing "ring".
Mal Meninga is despicable. I can still see this miserable pinhead whining that his sport (rugby league) had done nothing for him - nothing other than give him a national profile and a crapload of money, that is.

Even now, whenever I see him on TV I feel like throwing something at it. A whiny, pathetic, money-grubbing loser.
Now for a couple everyone's heard of. Tiger Woods. I
cannot stand him. Never could. And I agree with
JM1776 about Serena Williams; her range of excuses when defeated earn her full marks for creativity and zero for sportsmanship.