I know Nanaimoteuthis hasn't been found in rocks dating to the end of the Cretaceous, but the idea of a Tyrannosaurus rex encountering and battling a giant octopus is just so metal.
Would love to see something like this in a film someday.
So there's a new paper out that estimates a giant megalodon specimen at over 24 m long, suggests it could grow up to 28 m (blue whale size range!), lived close to a century and was eating basking sharks the way we eat anchovies (well maybe not on pizza, but you never know).