Boss Tease

Closely related to the abilitease, this preview boss battle is typically the plot excuse for losing your powers and needing to plow your way through lesser enemies to regain them.
 
In such games, the player may feel extremely cheated, because seemingly you really had the chance to destroy that pathetic boss from the get-go. The boss will retreat at the absolute last moment from their demise, perhaps taunting that you're being let off easy, or ordering the henchman after you because you're not a worthy opponent. And strangely, once the player reaches the end of the game, regained all of their hero's abilities, weapons, and power, the rematch will be a much more balanced fight, as if the boss had been equally training and grinding their way in preperation for your return all along. 
 
In some cases, the boss' new found power is the ability, weapon, or even race car taken directly from the player in the early stages.