Sometimes players foreshadow their own doom more effectively than you as a Dungeon Master ever could.
In a shared campaign that I am DMing, it came to the turn of character focused adventures. One character’s backstory mentioned he killed several people antagonizing him 10 years ago, giving him the nickname “Sev” (for seven). So of course, one of them survived and came back for revenge. Villain Finneous strolled into town and naturally learned everything about Sev and his adventuring party by doing the most dastardly thing possible: talking to NPCs. I think it went smashing, having a fiendish-powered warlock (and invisible familiar) threaten and kill friends and loved ones until the adventurers were nearly booted out of town because of the threats that followed them.
The real betrayal however was the DM listening to characters as they interacted during games. Especially one character that wanted revenge upon the people who stole his emotions and soul (as well as wanting a nightmare). So what does the DM do? Write up a contract and offer said played a new soul, a new patron (paladin/warlock), and a nightmare all for the low low price of abandoning his friends when they need to fight Finneous. The player said, “When else am I going to have the opportunity to have such a cool character moment?” Sev ended up dying in the confrontation with Finneous, but the player was immensely happy to have the game moments to showcase his character.
A good DM needs to be a fan of the characters. That does not mean a vorpal sword in every chest (though every chest should be a mimic), but it means really giving characters a moment to shine. I am not afraid to hurt the characters, but consent and buy-in from the players really does help. I have more character stories as the campaign continues, each one to challenge one of the characters with their past and future. I think the players are looking forward to what I throw at them.
Originally commission for Project: Fromage, the warforged colossus vs. tarrasque was really meant as a personal illustration. In the world of Eberron, I somehow found mecha and a kaiju for it to fight. Where will it end up? You might be surprised.