Movie : Jack the Giant Slayer

*

I felt disturbed by the movie title. The title is Jack the Giant Slayer. Jack is the hero in the movie, acted by Nicholas Hoult that reminded me of Merlin the series. I watched the movie with my family last weekend.

In the movie, he only killed at most 3 giants ; 

1) in the kitchen scene while rescuing Isabelle & Elmont, he dropped the knife on the giant's back, and the giant killed himself when he accidentally fell & pushed the knife deeper into his body ? ,

2) in the scene when he put the bee hive into the giant's iron mask and the giant fell back down to earth ,

3) in the final scene when he dropped the last bean into the giant's mouth *correct me if I am wrong.

All the scenes happened by luck. So what makes him be called as the Giant Slayer when in the end, he became the king for all the giants and probably would not kill any giants in the future? Why they did not just make the movie be called as Jack and the Bean Stalk or Jack and the Kingdom above the Sky or Jack the Lucky Giant's Slayer ? 

+

And why, instead of making all giants look so ugly and dirty, make them look decent and handsome perhaps? It is almost too cliché. Giants = ugly , giants = eat their own snot and smell their own armpit , giants = stupid.
But a giant with a retarded twin head on its shoulder - that was new :

*