القدير، القادر على كل شيئ، على كل شيئ قدير
The suggested translations are Pronounced:
AL-QADIR 'ALA KULLI SAHAY'
'ALA KULLI SHAY'IN QADEER
QADIR means "able," "capable," "powerful," or "mighty."
"Qadeer" is the intensive form of QADIR, so it answers to the omnipotence that the term "Almighty" implies.
The reason I provided three suggestions is that you provided no context (a full sentence or more of actual text where the expression is to be used). The context will determines which suggestion fits best.
If you want a one-word term, then AL-QADEER will do.
If you want something more expansive, then AL-QADIR 'ALA KULLI SHAY' may fit nicely.
In some contexts, 'ALA KULLI SHAY'IN QADEER may fit better.
American Heritage Dictionary; Al-Mawrid
Hans Wehr. A Dictionary of Modern Written Arabic