Ronin Network bridge hacked for ~$625M (173,600 ETH + 25.5M USDC)

On March 23, 2022, attackers drained roughly $625 million from the Ronin bridge underpinning the Axie Infinity play-to-earn game, the largest crypto hack on record at the time. The theft hinged on five of nine validator keys being compromised, including one access grant from a 2021 event that was helpfully never revoked, and went unnoticed until a user failed to withdraw funds six days later. The FBI later pinned it on North Korea's Lazarus Group.