The other thread about favorite mechanics is great, so let’s also do the opposite: what are some of your most hated mechanics?
Pay 2 win and excessive abuse of FOMO.
E.g. for the next two weeks you can purchase/grind for [character] with a LIMITED EDITION green hat!
It would be OK if such thing was behind an achievement and allowed to be gained later.
Some companies have gotten a little sneaky with it, like Microsoft with age of empires. They make their newly released DLC civs overpowered for two months then nerf it every time.