What is the most alchoholic beverage?

Straight grain alcohol.

I'm sure there is some pretty potent home-made specialties around (namely in my storeroom, oh, and that bottle of Absinthe I have that no-one has claimed---long story..) but here is an extract from our pal wiki:

"Everclear, a neutral grain spirit is sold at 190 proof in parts of the U.S. where it is legal. For comparison, absinthe (one of the highest-alcohol commercial liquors available) usually tops out at around 70% ABV and ranges from about 120 to 130 proof. Austrian Stroh 80 rum is an exception with a ABV of 80% (proof 160)."

https://en.wikipedia.org/wiki/Alcoholic_proof

Probably grain alcohol, also known as ethyl alcohol, pure grain alcohol and grain neutral spirits. Usually about 190 proof, or 95% alcohol.

Moonshine or Grain alcohol.

https://en.wikipedia.org/wiki/Moonshine

As for bottled, legitimate, over the counter beverages, Bacardi 151 is still reigns supreme.

https://en.wikipedia.org/wiki/Bacardi_151


Strongest Commercial Alcoholic Drink
The strongest commercially available alcoholic drink dates from during the first half of the 20th century, when the Estonian Liquor Monopoly marketed a beverage that was distilled from potatoes. It was 196 proof (98% alcohol). Estonia is one of the Baltic states.

http://www.calwineries.com/blog/2007/03/12/dear-guinness-book-of-world-records-where-s-the-alcohol-entries

Everclear, which is bottled and over the counter, has more alcohol than 151.

Everclear is not available in ALL states. Unfortunately!