Just some physics facts about definitions. Terminal velocity is often loosely used to refer to the speed when the force of gravity balances the drag in the opposite direction in freefall. So strictly terminal velocity is a vector in the direction that gravity is pulling, where the magnitude of that vector is the terminal speed that gives a drag force equal numerically to the downward force due to mass of the object being considered.
If you want to consider energy then you can take the linear kinetic energy (mass times the square of the speed) as a major component, but if there is rotation then there is rotational kinetic energy equal to the moment of inertia of the system times the square of the magnitude of the angular velocity. Clearly the rotation of the entire airframe would contribute but also rotation of say, spinning turbines at high speed could also be a component. Rotation axes in different directions could lead to transfer of rotational energy between different modes. Apart from these contributions to total kinetic energy there is also some energy in vibration of massive components as well but likely to be numerically less significant. Of course there is stored energy in unburned fuel that can be released as well.
The various elements of kinetic as well as potential energy can then be dissipated into destructive rupture, distortion and other failure modes on impact (as well as a small amount to heat and sound). This is a physics perspective as a general consideration applying to any accident in the air.