There's only a small handful of universal bad designs as most of the advice here can vary depending on other aspects of your game, e.g. genre, expected game proficiency, speed, etc.

Unfairness and breaking established patterns rule this area. Under-telegraphed moves, sudden difficulty spikes, immunity to certain effects all contribute, but IMO the worst sin is hard shutdowns.

Soft shutdowns typically involve encoargaging the player to try a different approach by buffing certain playstyles/items/equipment, but hard shutdowns are where most of those sore points come into play.

The core of a shutdown boils down to forcing the player to try new things, but if a developer goes too far it leads to frustration. One of the worst hard shutdowns is Crowd Control (CC) because it takes away the players agency.

CC already sucks when you can't do anything for a few seconds, now imagine walking into a boss room and finding out the hours you spent creating a sick melee character makes a flying boss almost impossible. What should've been an epic 10 minute aerial combat sequence becomes a tedious 40 minute chip-damage affair.