Title says it all. What words does your mind tell you something means even if you know it’s the opposite? For me, it’s dearth. I know it means a lack of something, but my mind always wants to jump to it meaning plenty of something.
Drives me crazy and makes it hard to read sentences using it.
For years, I had the same trouble with “opaque,” but I think I’ve finally trained myself out of thinking its a synonym for “transparent.”
“Preceding”, especially when there were TV spots that said “the preceding message was brought to you by Major League Baseball”.
Building get razed when they are torn down? But the Amish have barn raisings when they finish building a new barn? 
INflamable means FLAMABLE!!?!
Penultimate means second, I eventually realized.
“Spendthrift” sounds like it describes someone who is thrifty. Quite the opposite, actually.
Not quite per the OP, but the phrase “discovered to be missing” makes me want to run from the building screaming.
“Sanction.”
I get confused with “dearth” sometimes, too.
Also, “nonplussed.” It means confused or at a loss but I always think of it as meaning someone who just doesn’t care. Or like, an adjective form of, “Meh, whatever.” Maybe I’m getting it mixed up with “nonchalant”?
Sanguine sounds to me as though it should mean cool and calm when it means quite the opposite.
Third me for “dearth”.
I get confused with “dubious”. It sounds prestigious doesn’t it?
No, it means the exact opposite. It means second-to-last.
Joe
Of course, you’re right. I most always heard it used as “the penultimate of the season” and I thought it meant last, until a few years ago.
How is “cheerfully optimistic, hopeful, or confident” the opposite of cool and calm?
Enervate sounds as if it should mean the same thing as energize. Doesn’t.
“Fitful,” when describing a night’s sleep.
I bet you don’t like restive either 
Dearth is also the word I have the most trouble with. I always have to ask myself if it means excessive amounts or not enough.
Decadence, on the other hand, is the one I find the most confusing. How can a word that means excessive self indulgence also mean falling into a state of decay? I can see how the former could contribute to the latter, but it’s weird to use the same word for both.
Crepuscular can be used to describe things that are associated with twilight (the time, not the movie), but really it should be used to describe purulent, festering wounds.
love
yams!!
I always thought epitome meant the most outstanding example of something but it means a perfectly average example of something.