Which speakers did you find bright, fatiguing or just disappointing in some way?

There are no absolutes. Everything posted so far is purely anecdotal.

I just recently listened to a speaker that sounded harsh and fatiguing on one particular amp and then simply glorious and unparalleled on another amp. Not to even mention the myriad of other components that play a role. 
It is not necessarily the speaker, it is rather how they matched up with certain components.

I have owned a pair of Klipsch RP-5000 and I have auditioned the Forte IIIs. I found them both to be hard to listen to for long periods of time. The La Scalas I auditioned had a nice airy sound to them, but the sound stage and imaging were lacking. Many people say that Focals are bright. I have not found this to be true. I can listen to my Aria 936s all day and they never annoy. I power them with a Hegel H390 and use a Audiolab 6000CDT transport played through the Hegel DAC.
Speakers I have owned:
Infinity Kappa 7    Klipsch RP-5000     KLH Kendall      Focal Aria 936

Focal Aria. Lacquer finish had orange peel to it. Detail in speakers were great, but the range of the speaker didn't seem to come together. A lack of unity between frequency. 

I recently home auditioned the highly lauded KEF LS50 Meta with McIntosh solid state and hybrid amplification. They were listenable but didn’t wow me. They lacked high-end presence and the sound was just kinda boring. Perhaps because I’m used to them, but I much preferred my old DefTech SM-450s in my smallish room.

@bdgregory 

I heard what I heard, and have no reason to make it up. Not sure why you think my claim dubious.

I didn't suggest that you made up the claim. I simply found it odd, given both my experience, and the relative lack of similar opinions from other owners whose feedback I have read.