Blurt is nice

however... there's already a word for it:
Starts with W, and sounds like 'anchor'.
Although, a nice technical term which serves quite well is: rectum.
This has several aspects, and works remarkably well...
"Well, xxx is an absolute rectum. They ruined the effect."
So, the meanings:
LITERAL: rectum = a***hole
PLAY ON WORDS: rectum = 'wrecked 'em', as in, ruined them.
LATIN: rectus = latin word for straight... as in, these 'blurters' get 'straight to the point and reveal the methods'.
VULGAR: rectum = quite a nasty word!
MEDICAL/METAPHORICAL: rectum in medical terms is the last few inches of the intestine where poo is stored before it's final release to the world. Therefore, badging someone a 'rectum' means that they are 'full of poo?'
So, I vote either a 'blurt' or a 'rectum'.