4 most off flavors

All you Judges out there, am thinking of presenting this to my Brew club so we can identify them. What are the 4 off flavors mostly found in the beers you judge?
  I plan to set up so we can taste them and  learn the 4 most prominent ones and learn from that. If  we do all of them it seems it will be harder to remember what they are, so I figure doing one at a time over and over again should improve our taste buds.

Diacety lis #1 by far for me.  Fusels and phenolics would be in my top 4.  Not sure after that.

Diacetyl, oxidation, phenols, solventy (or hot alcohol) for most common off flavors I encounter.

Astringency first and foremost, in terms of flaws, though it is not a flavor.  Cloying sweetness would be up there, too.

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MY RESPONSES, in no particular order:

Diacetyl, DMS, chlorophenol, oxidation.

I totally agree with this too.  Hot alcohol, solvent, and OMG cloying sweetness yeah that happens a lot too.

Agree with Dave on this one.  Diacetyl (although I am a bit nose blind and taste blind to it, but have found a way to detect it better), DMS, phenols, get that one right away, and solventy.  I also have a very sensitive palate to sulfur which I find in lagers that have not fermented out completely.

Since these bad flavors are identified, what is the root cause and how do we avoid this in our beer?

Thank you everyone for the feedback. This was a great help.

The warmer the climate you live in, the more you taste excessive fruity esters and phenols. That peach thing from US-05 is pretty common, as is the rotten fruit salad thing that about every English yeast gives you when fermented at around 78F – usually paired with a fine bouquet of fusels and sometimes “extract tang” from old LME.

Off flavors… you mean like chocolate, peanut butter, coffee, doughnuts etc?  ;D

Now wait a minute…you have gone too far!
In my house, those are staples.

:smiley: