Bitcoin whales realized approximately $4 billion in profits yesterday, marking the largest single-day gain since February, according to CryptoOnchain data. Mega-whales holding over 10,000 BTC accounted for $2.17 billion of the profits, while large whales with 1,000 to 10,000 BTC generated $1.25 billion. This surge in realized profits suggests significant selling pressure near local highs, posing a potential concern for short-term traders.