Green’s Dictionary of Slang

mighty, great.

1824		T. De Quincey Works (1871) XVI 261: Such rubbish, such ‘almighty’ nonsense (to speak transatlanticè), no eye has ever beheld [F&H].
1836		T. Haliburton Clockmaker I 23: That everlastin’ almighty villain, Van Buren.
1879		Besant & Rice ‘The Seamy Side’ in Appleton’s Journal (N.Y.) Nov. 407: I am quite sure that he got into such an Almighty Funk at last, that he forgot all about his tenses and moods.
1889		B. Mitford Fire Trumpet I 104: If you don’t kill yourself with almighty blue fits, call me a nigger.
1955		H. Ainley In Order to Die 210: [T]here came a series of almighty explosions from just behind him .
2018		J.-P. Jordan Joys of War 6: . An Irishman, a shitload of beer, a pair of skis and some steep hills were an almighty combination .