What's the highest House edge you've ever seen? I'm talking about any game and any bet, be it a table game, a slot machine, a side bet, ...
At the casino nearest to where I live, in Switzerland, there's a Oasis poker (caribbean stud poker where you can exchange a card if you pay again the ante) with a side bet of 1 Fr which pays you 10000 fr if you have a royal flush, 1000 if you have a straight flush, 500 four of a kind, 250 full house, 100 flush, for an house edge of 60.84% (bonus doesn't get paid if you exchanged a card)
At the casino nearest to where I live, in Switzerland, there's a Oasis poker (caribbean stud poker where you can exchange a card if you pay again the ante) with a side bet of 1 Fr which pays you 10000 fr if you have a royal flush, 1000 if you have a straight flush, 500 four of a kind, 250 full house, 100 flush, for an house edge of 60.84% (bonus doesn't get paid if you exchanged a card)