Everything goes better with Batman, right? Well, no. Not if Batman can't kill. In 2008, MK teamed up with DC to produce a game where the roster was split between famous superheroes/villains and Mortal Kombat mainstays. It was gimmicky but ultimately a fine enough addition to the canon. After all, there's an innate glory in watching Scorpion fight Batman. The problem as far fatalities go is that this was one of the lamest entries in the entire franchise, because the DC heroes weren't allowed to kill. Superman, Batman, Flash, Wonder Woman, Green Lantern - they've all got principles against offing anyone for good, which limited them to performing tamer Heroic Brutalities.
The violence was toned down considerably in general, the game receiving a Teen (T) rating from the ESRB, rather than its usual M. Rabid fans were not best pleased, and therefore these Heroic Brutalities have not been considered for this list - they're just TOO tame. Kano's finisher on the other hand still technically killed his opponents, but it brings shame to the name 'Fatality'.
It's the weakest in the game, possibly of all time - even more so than Liu Kang's uppercut from Mortal Kombat 1; at least that showed some blood. In this one, Kano rolls his opponent onto their back, then jumps on their chest once. That is the sum total of the damage he caused. Then the voice booms 'Fatality' and everyone is left confused, angry, or combination of the two. Just terrible.