A few people mentioned that the quick-slash attack looked like it wasn't very hard to dodge. So I went and fixed that.
The slash lines are now weighted toward the screen's center a bit more, there are 4 more slashes, and it all goes 25% faster.
Also, a sword boss wouldn't be complete without a spinny attack:
All that's left now is to tie the attack sequences together and put in an outro animation. After that, I think it's finally time to address the controls... Stay tuned for another post on that matter.