"The MEV Searcher"

These are the most technical and often considered "evil" predators. They use sophisticated bots to monitor the Mempool (a waiting area for unconfirmed transactions). If you buy a large amount of a coin, their bots will see your transaction, then quickly buy that coin right before you (raising the price), and sell it to you at a higher price (Sandwich Attack). They take small amounts of money from your pocket without you even realizing it.