Beast Mode is when they’re all dirtied up with ungainly, heavy stuff (which would negate stealth) mounted on the external pylons.
Beast Mode? The F-35 will never be a beast. It is a least visible, early entry, stealth weapon.
The B-52 and the B-1B and the B-2 are Beast aircraft.
And as far as ground troops are concerned the lowly AC-130H is a Beast. And to the troops on the ground cheer the A-10 Warthog when they arrive.
Beast? Heavy metal attack.