Bitcoin (BTC) saw lows of under $45,600 on Aug. 15 as a second instalment of its resistance rejection played out. BTC/USD 1-hour price chart (Bitstamp). Source: TradingViewAnalysts eye BTC attack on all-time highsData from Cointelegraph Markets Pro and TradingView showed BTC/USD giving up $46,000 overnight on Saturday after an earlier failed breakout. As Cointelegraph reported, bulls had run out of steam during an attack on a major sell wall holding Bitcoin back from $50,000.The U-turn sparked a more fragile mood for Sunday, with daily losses sitting at 4% at the time of writing.”This area is to me the major boss and hurdle to climb,” popular Twitter trader Pentoshi warned, adopting a bullish view on higher timeframes. BTC/USD, he added, had almost completed preparation for a rematch of all-time highs in a zone above resistance at $50,000 and higher.”I still believe for now it will be a Short term LH on the micro before we go for that upper range.”Fellow trader, analyst and Cointelegraph contributor Michaël van de Poppe likewise hinted about a longer-term moment of reckoning potentially appearing soon.”Bitcoin is inside the higher timeframe resistance,” he tweeted Saturday. “Next week will be the important week, I think.”Buy and sell levels on major exchange Binance showed the $48,000 sellers still firmly in place, with support amassing at $45,000 after the modest leg down.BTC/USD buy and sell levels (Binance) as of Aug. 15. Source: Material Indicators/ TwitterCardano cools major rallyThe Bitcoin had a conspicuous knock-on effect among major altcoins.Related: XRP chart triggers sell-off warning after price explodes by 54% in one weekWhile many in the top-fifty cryptocurrencies by market cap either canceled out or saw weak 24-hour gains, the top five all lost in step with BTC.Cardano’s ADA token, the standout along with XRP as the weekend began, came off multi-month highs to circle $2.10.”Would I be buying Cardano here? No,” Van de Poppe cautioned prior to the dip. “Do I expect Cardano to be gaining value in the coming months/years? Yes.”Market participants continue to expect altcoin opportunities to increase in the coming months, with a focus on DeFi tokens in particular.