Answer:
Orcinus Orca, an apex predator, is the largest of the Delphinidae Family, but their Suborder Odontoceti identifies them as "toothed whales" and their Order Cetacea identifies them as whales. Dusky dolphins are also of the Order Cetacea and so, are, technically, toothed whales.
The Killer Whale name is actually a translational reversal, in that they are in fact, Whale Killers. They are known to kill other, larger whales, and not eat them. They are also known to separate young whale calves from their mothers and eat them while they sink.