The most common and most likely answer to this crossword clue is the 4 letter word ZEUS
I've seen this crossword clue in The Times
Z
E
U
S
More clues leading to the result ZEUS
- Great being in Greece, where crisis was once reversible
- From East, call on unknown god
- God! Middle East crisis is mounting
- One almighty petition letter after all the others sent back
- Rising canal reveals God
- He or she with the Guardian who tormented 24
- God and Eden’s downfall rejected
- Unknown petition backing god
- Character in Greek mythology taking back Egyptian port
- 20 in elevated Egyptian city
Buddy explains!
The straight part
We know that "One almighty" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one almighty = zeus.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.