Which tactic would have been MOST likely to have been found in World War I and NOT World War II?

The major difference was in the use of tanks in mass scale and in schwerpunkt operations, in combination with the advent of mass aircraft, resulting in the German Blitzkrieg doctrine.

The armour was a response to the machinegun that dominated the killing fields of WW1. WW2 also focused much more on mobility rather than sheer firepower, best described in the German offensive against France, and the German retreat against overwhelming soviet artillery (where the Germans evacuated the trenches meer hours before gigantic soviet barrages began, leaving the soviets with a poor result other than gaining a few km). Interestingly, the tactic favoured by Hitler in the beginning, mobility, he despised in the middle and end of the war, where he resorted to static defenses despite his generals recommendations.