LONDON/SINGAPORE—Bitcoin plummeted as much as 17 percent on Tuesday as investors grew nervous at sky-high valuations, triggering the liquidation of leveraged bets and sparking a sell-off across cryptocurrency markets. The world’s biggest cryptocurrency was facing its biggest daily drop in a month, falling to as low as $45,000. In choppy trading, it was last down 15.6 percent. The drop took its losses to over a fifth from a record high of $58,354 hit on Sunday and underscored the volatility of the emerging asset—though it is still up around 60 percent this year. “The kinds of rallies we’ve been seeing aren’t sustainable and just invite pullbacks like this,” said Craig Erlam, senior market analyst at OANDA. “It was an extremely overbought market.” Ether, the world’s second largest cryptocurrency by market capitalization that often moves in tandem with bitcoin, also dropped more than 20 percent to $1,410, down over 30 percent from …