Baldur's Gate 3 has some pretty evil and hateful bad guys. There's Aunty Ethel the hag in disguise; Orin, who literally lusts for torture and murder, and the Dead Three who are pulling all the strings. Worse than them is Wulbren Bongle, who is easily the most hated character in the game.
If you're thinking about going back to Baldur's Gate 3, the final patch is a perfect excuse.
However, when it comes to being purely malicious, evil, and manipulative, there is one character that sits atop the perch. Over the course of Act 2, you'll come across a Blue Jay that seems like it's in distress. It will ask you to help take back its nest from some eagles, but don't you even once fall for it. This vile bird is the most dangerous threat to the Sword Coast.
If you know nothing about birds, you may be inclined to help the Blue Jay by wiping out those mean eagles. However, Blue Jay by nature are known to take over other birds' nests. If you play out the quest or talk to the eagles, you'll learn that the Blue Jay really wanted you to wipe out the eagles so...