the Mighty One: an old title for God as the sheer strength standing behind Jacob's family, and used of no one else
This word turns up only six times, and always in the same shape: bound to a name, either "the Mighty One of Jacob" or, once, "the Mighty One of Israel." It is a title for God and nothing else. No king, no army, no animal is ever called this.
The title belongs to the oldest layer of Israel's memory of God. It first appears in Jacob's blessing over Joseph in Genesis 49:24, where God's strength is what steadies the archer's hands. Later writers reach back for it on purpose. David swears his vow to the Mighty One of Jacob in Psalm 132:2 and 132:5, and Isaiah twice closes a promise of rescue with it: "I, the LORD, am your Savior and your Redeemer, the Mighty One of Jacob" (Isaiah 49:26; 60:16). Isaiah 1:24 is the one place where the tone flips, and that same strength is aimed at Israel's own corrupt leaders.
A near twin, אַבִּיר, is written with the same letters and differs only in the small vowel marks under them. That one is the ordinary word for brute strength, and it gets used of bulls, war horses, and strong men. The two spellings are kept apart on purpose, so that the form used of God is never the form used of an animal. Some scholars have argued that the title once pictured God as a bull, the strongest animal a herding family knew, but most now hold back from that, since this particular form is never used of an animal anywhere in the Bible.
It sits alongside the other ancient names for God carried down from the family stories, above all שַׁדַּי, "the Almighty." That title speaks of a power that can bless or break. This one is simpler and more personal: raw strength tied to one family's name, the strong one who belongs to Jacob.