This is a Question "You" have no doubt have wondered about many times...and I can assure you.....that the answer is Very re-assuring...
There are No Documented cases of attacks on humans resulting in the killing of humans on purpose.
The Main Reasons for "So Called" Whale Attacks on humans are...
Wrong place - Wrong Time
There is a known case of an accident when a whale "jumped" or "breached" out of the water and landed on a kayak - but you can imagine how rare that is!
There have been a up to 24 incidents in captivity where an Orca Whales have injured or killed trainers - but the reasons for these still quite rare occurrences were not clear.
One reason I believe is that these whales are actually housed in a "whale jail" of sorts and get bored with the same routine and want to "play" with the trainer - not realizing humans can not hold their breath like they do.
For Example: - In this VIDEO CLIP - below -
......a Pilot Whale unaccustomed to the presence of divers thought the female diver was a "play thing" and dragged her down till it realized she was running out of air and quickly rushed her to the surface and let her go.
......even here you can see the intelligence of these large creatures..... but we have to be very, very careful around all wild animals - they can be unpredictable.
This is the closest any human has come to being "attacked" by a wild whale...and you can tell by the video - it was not trying to harm the diver.
Orca Whales or Killer Whales - have come close to attacking a human a couple of times - once when a child was playing close to the shore - but when the Whale realized it was not a seal - it quickly aborted to attack....
...another instance when the Orca Whale thought a surfer was a seal....and again aborted the attack.
Killer Whales are very intelligent mammals and can tell the difference as soon as they get close enough to realize we are not on their menu......
And one time when a Sperm Whale somehow came into a small cove in Japan - three men in a boat were trying to chase the whale out to sea by making noise but the whale ignored their attempts and for some mysterious reason rammed their boat twice and as a result one man drowned......afterward it swam out to sea.
Researchers don't know what caused this ordinarily docile creature to purposely hit the boat - but any time a whale comes into shallow water - it is not a healthy sign - usually something is wrong with the whale.