Erika helping Selene escape the mansion. Okay, maybe it wasn't completely altruistic, but she'd spent the whole movie as a sycophant to Kraven.
Selene: "Why are you helping me?"
Erika: "I'm not. I'm helping me."
Viktor killing a werewolf through simply slapping him
Michael outspeeding Viktor through about half of the final battle
Selene slicing Viktor's head in half with his own sword. Icing on the cake: she shows him the blade with his blood on it before he dies.
The double kill of Markus and William in Evolution. First, Hybrid!Michael rips the top half of William's head off as Markus watches in despair. Then, right after he taunts Selene, she rips off the pointed tip of his wing, stabs him through the chin, then pushes him into the blades of a fallen helicopter, turning him into little vampire chunks.
Rise of the Lycans had a few more. In addition to Raze winning a fist fight with a couple wolf-form lycans before he is turned, there's the climactic scene with Lucien and Victor.
Victor: "I should have crushed you under my heel the day you were born!"
Pretty much every action scene in Underworld: Awakening, especially Selene vs the Uber-Lycan
One would think that Eve, Selene's daughter was a goner when the werewolf had its jaws on her throat. Seconds later she rips its skull in half.
The van carrying Selene's daughter is driving out of the building. Out of nowhere Selene appears and slams into the van like a football player making a tackle, flipping the van over and causing it to slide clean across the garage.
Eve kills Lycan-form Lane after a vicious fight by ripping out his throat.