For example, “flammable” and “inflammable” both describe an object that can easily catch on fire. I can also think of “ceased” and “deceased”, both of which can mean someone or something has been brought to an end.
edit: Some people are including words that can also mean its opposite (like sanction or table), those are cool too! The more weird words, the better!
Sanction can mean a punishment or an authorization.
Came up in a DND game where a devil’s contract said the players crossing the region would be sanctioned, or something like that. Players thought it meant they had permission, fine print said they would be punished.
It means authorized decision. The decision can be a punishment.